diff --git a/NEWS b/NEWS
index 176214812..9ff0845ff 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,7 @@ Enhancements
  - [web] updated Angular to version 1.7.7
  - [web] restored support for next/previous slot suggestion in attendees editor
  - [web] improved auto-completion display of contacts
+ - [web] allow modification of attendees participation role
  - [core] baseDN now accept dynamic domain values (#3685 - sponsored by iRedMail)
  - [core] we now handle optional and non-required attendee states
 
diff --git a/UI/Scheduler/English.lproj/Localizable.strings b/UI/Scheduler/English.lproj/Localizable.strings
index fb3168ece..b3c304290 100644
--- a/UI/Scheduler/English.lproj/Localizable.strings
+++ b/UI/Scheduler/English.lproj/Localizable.strings
@@ -440,15 +440,45 @@ validate_untilbeforeend    = "The recurrence must end after the first occurrence
 "Are you sure you want to delete the selected components?"
 = "Are you sure you want to delete the selected components?";
 
-/* Legend */
+/* Participation role */
+"Role" = "Role";
+
+/* Participant role: participation is required */
 "Participant" = "Participant";
+
+/* Participant role: participation is required */
+"req-participant" = "Participant";
+
+/* Participant role: participation is optional */
 "Optional Participant" = "Optional Participant";
+
+/* Participant role: participation is optional */
+"opt-participant" = "Optional Participant";
+
+/* Participant role: participant is copied for information purposes only */
 "Non Participant" = "Non Participant";
+
+/* Participant role: participant is copied for information purposes only */
+"non-participant" = "Non Participant";
+
+/* Participant role: participant is chair of the calendar entity */
 "Chair" = "Chair";
+
+/* Participant role: participant is chair of the calendar entity */
+"chair" = "Chair";
+
+/* Participant status: needs action */
 "Needs action" = "Needs action";
+
+/* Participant status: event accepted */
 "Accepted" = "Accepted";
+
+/* Participant status: event declined */
 "Declined" = "Declined";
+
+/* Participant status: tentatively accepted */
 "Tentative" = "Tentative";
+
 "Free" = "Free";
 "Busy" = "Busy";
 "Maybe busy" = "Maybe busy";
diff --git a/UI/Templates/SchedulerUI/UIxAttendeesEditor.wox b/UI/Templates/SchedulerUI/UIxAttendeesEditor.wox
index b07861c40..f49067f6a 100644
--- a/UI/Templates/SchedulerUI/UIxAttendeesEditor.wox
+++ b/UI/Templates/SchedulerUI/UIxAttendeesEditor.wox
@@ -4,6 +4,7 @@
     xmlns:var="http://www.skyrix.com/od/binding"
     xmlns:const="http://www.skyrix.com/od/constant"
     xmlns:label="OGo:label"
+    xmlns:rsrc="OGo:url"
     >
   <script type="text/javascript">
     var dayStartHour = <var:string value="dayStartHour"/>;
@@ -51,6 +52,16 @@
                    ng-click="editor.removeAttendee(currentAttendee, eventForm)">
           <md-icon>remove_circle</md-icon>
         </md-button>
+        <md-button class="md-icon-button"
+                   label:aria-label="Role"
+                   ng-click="editor.component.$attendees.nextRole(currentAttendee)"
+                   ng-switch="currentAttendee.role">
+          <md-tooltip md-direction="right">{{ currentAttendee.role | loc }}</md-tooltip>
+          <md-icon class="ng-animate-disabled" ng-switch-when="req-participant">record_voice_over</md-icon>
+          <md-icon class="ng-animate-disabled" ng-switch-when="opt-participant">person_outline</md-icon>
+          <md-icon class="ng-animate-disabled" ng-switch-when="non-participant" rsrc:md-svg-src="img/voice_over_off.svg"><!-- non-participant --></md-icon>
+          <md-icon class="ng-animate-disabled" ng-switch-when="chair">event_seat</md-icon>
+        </md-button>
         <sg-avatar-image class="md-avatar"
                          sg-email="currentAttendee.email"
                          size="40">person</sg-avatar-image>
diff --git a/UI/WebServerResources/img/voice_over_off.svg b/UI/WebServerResources/img/voice_over_off.svg
new file mode 100644
index 000000000..6a1ccf260
--- /dev/null
+++ b/UI/WebServerResources/img/voice_over_off.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M12.99 9.18c0-.06.01-.12.01-.18 0-2.21-1.79-4-4-4-.06 0-.12.01-.18.01l4.17 4.17zm-6.1-3.56L4.27 3 3 4.27l2.62 2.62C5.23 7.5 5 8.22 5 9c0 2.21 1.79 4 4 4 .78 0 1.5-.23 2.11-.62L19.73 21 21 19.73l-8.62-8.62-5.49-5.49zM9 15c-2.67 0-8 1.34-8 4v2h16v-2c0-2.66-5.33-4-8-4zm7.76-9.64l-1.68 1.69c.84 1.18.84 2.71 0 3.89l1.68 1.69c2.02-2.02 2.02-5.07 0-7.27zM20.07 2l-1.63 1.63c2.77 3.02 2.77 7.56 0 10.74L20.07 16c3.9-3.89 3.91-9.95 0-14z"/><path fill="none" d="M0 0h24v24H0V0z"/></svg>
\ No newline at end of file
diff --git a/UI/WebServerResources/js/Common/Common.app.js b/UI/WebServerResources/js/Common/Common.app.js
index b37995fe9..1df505957 100644
--- a/UI/WebServerResources/js/Common/Common.app.js
+++ b/UI/WebServerResources/js/Common/Common.app.js
@@ -139,8 +139,11 @@
   /**
    * @ngInject
    */
-  configure.$inject = ['$logProvider', '$compileProvider', '$httpProvider', '$mdThemingProvider', '$mdAriaProvider', '$qProvider'];
-  function configure($logProvider, $compileProvider, $httpProvider, $mdThemingProvider, $mdAriaProvider, $qProvider) {
+  configure.$inject = ['$animateProvider', '$logProvider', '$compileProvider', '$httpProvider', '$mdThemingProvider', '$mdAriaProvider', '$qProvider'];
+  function configure($animateProvider, $logProvider, $compileProvider, $httpProvider, $mdThemingProvider, $mdAriaProvider, $qProvider) {
+    // Disabled animation for elements with class ng-animate-disabled
+    $animateProvider.classNameFilter(/^(?:(?!ng-animate-disabled).)*$/);
+
     // Accent palette
     $mdThemingProvider.definePalette('sogo-green', {
       '50': 'eaf5e9',
diff --git a/UI/WebServerResources/js/Scheduler/Attendees.service.js b/UI/WebServerResources/js/Scheduler/Attendees.service.js
index d7ef8c277..3685c7b76 100644
--- a/UI/WebServerResources/js/Scheduler/Attendees.service.js
+++ b/UI/WebServerResources/js/Scheduler/Attendees.service.js
@@ -32,7 +32,7 @@
    * @desc The factory we'll use to register with Angular
    * @returns the Attendees constructor
    */
-  Attendees.$factory = ['$q', '$timeout', '$log', 'sgSettings', 'Preferences', 'User', 'Card', 'Gravatar', 'Resource', function($q, $timeout, $log, Settings, Preferences, User, Card, Gravatar, Resource) {
+  Attendees.$factory = ['$q', '$timeout', '$log', 'sgSettings', 'Attendees_ROLES', 'Preferences', 'User', 'Card', 'Gravatar', 'Resource', function($q, $timeout, $log, Settings, ROLES, Preferences, User, Card, Gravatar, Resource) {
     angular.extend(Attendees, {
       $q: $q,
       $timeout: $timeout,
@@ -42,7 +42,8 @@
       $Preferences: Preferences,
       $Card: Card,
       $gravatar: Gravatar,
-      $$resource: new Resource(Settings.activeUser('folderURL') + 'Calendar', Settings.activeUser())
+      $$resource: new Resource(Settings.activeUser('folderURL') + 'Calendar', Settings.activeUser()),
+      ROLES: ROLES
     });
 
     Attendees.dayStartHour = parseInt(Preferences.defaults.SOGoDayStartTime.split(':')[0]);
@@ -62,9 +63,14 @@
     angular.module('SOGo.SchedulerUI', ['SOGo.Common']);
   }
   angular.module('SOGo.SchedulerUI')
+    .constant('Attendees_ROLES', {
+      REQ_PARTICIPANT: 'req-participant',
+      OPT_PARTICIPANT: 'opt-participant',
+      NON_PARTICIPANT: 'non-participant',
+      CHAIR: 'chair'
+    })
     .factory('Attendees', Attendees.$factory);
 
-
   /**
    * @function timeToQuarters
    * @memberof Attendees
@@ -138,7 +144,7 @@
             attendee = {
               name: ref.c_cn,
               email: ref.$preferredEmail(options? options.partial : undefined),
-              role: 'req-participant',
+              role: Attendees.ROLES.REQ_PARTICIPANT,
               partstat: 'needs-action',
               uid: ref.c_uid,
               $avatarIcon: 'person',
@@ -165,7 +171,7 @@
           isMSExchange: card.ismsexchange,
           name: card.c_cn,
           email: card.$preferredEmail(),
-          role: 'req-participant',
+          role: Attendees.ROLES.REQ_PARTICIPANT,
           partstat: 'needs-action',
           $avatarIcon: card.$avatarIcon
         };
@@ -183,6 +189,20 @@
     }
   };
 
+  /**
+   * @function nextRole
+   * @memberof Attendees.prototype
+   * @desc Switch the attendee to the next participation role.
+   * @param {Object} attendee - the attendee definition
+   */
+  Attendees.prototype.nextRole = function(attendee) {
+    var roles = _.values(Attendees.ROLES);
+    var index = _.findIndex(roles, function(role) {
+      return attendee.role === role;
+    });
+    attendee.role = roles[++index % 4];
+  };
+
   /**
    * @function hasAttendee
    * @memberof Attendees.prototype
diff --git a/UI/WebServerResources/js/Scheduler/ComponentController.js b/UI/WebServerResources/js/Scheduler/ComponentController.js
index 0dd0ee88c..06dff7bf7 100644
--- a/UI/WebServerResources/js/Scheduler/ComponentController.js
+++ b/UI/WebServerResources/js/Scheduler/ComponentController.js
@@ -234,6 +234,8 @@
         oldEndDate = new Date(this.component.end.getTime());
       if (this.component.due)
         oldDueDate = new Date(this.component.due.getTime());
+
+      $timeout(scrollToStart);
     };
 
     this.addAttachUrl = function () {