With Astrea Task Creator for Salesforce CRM, available on AppExchange, it becomes easy to create task that can be assigned to multiple users, for Custom and Standard objects. You can download the component from Salesforce Appexchange.
There are two way of doing assignment of task to multiple Users:-
- Single tab name : "Create task"
- Quick Actions on few standard objects: like Account,contact and lead.
Astrea task creator provides a way to perform this in lightning by providing a Quick Action. Admin can drag and drop the action to the specific layout. There is a custom lookup icon, that will allow end user to select “multiple Users” from "public groups", "Roles", "Roles and Subordinates" and on individual user basis.
You can also refer the User Manual for further details, from here.