Participants page: selecting multiple users with different filters not possible

Hi,

Initial functionality in 3.4:
in Moodle 3.4 it was possible to select some users from the participants page and then select the "Send message" option. Then, a new page opened and there the user had the possibility to search for further users to add to the current recipients list or to delete users from that list.

Regression:
In MDL-59758 this behavior was changed to use a less complicated modal dialogue. In that dialogue the user can only type in his message and send it or cancel the dialogue entirely. Because the link to add further users is gone now and the initial filtering is insufficient, this functionality is lost entirely.

Possible solution:
As it's not intended to get the missing link back into the cleaner modal dialogue, the correct solution would be to improve the filtering of the participants page. If the user can initially filter the list to fit his needs and then easily select all the recipients he wants to contact, there's no need for a dedicated "Add further users" list.

The issues (no sake of completeness) with the current filtering behavior are:

• It's not possible to select more filters of the same type (MDL-60688). For example, I want to select users from "Group 1" and from "Group 2", I can only select one group at once. The other filter will be deleted with the new filtering of the same type.
• It's not possible to add other logical connections than the default AND connection. For example: I want to message members of "Group 1" and some of the non-edting teachers. In that case I can select both filter types (groups and roles), but this will lead to 0 results if the non-editing teachers are not members of "Group 1" at the same time.
  In that case it would be necessary to combine the two filters in that case with an OR connection and not with an AND connection.
  So the filters should be combinable with brackets and more logical connections.

Best, Kathrin