We found that if you configure the agile board to use swim lanes by assignee is possible to drag and drop to other users a given task, so the task is now assigned to him.
However if a user currently hast not assigned tasks there is not swim line to drop in a task to assign it to him.
Is it possible to enable in swim lanes to show groups that currently do not have any issues?.
I do not know if this is related to the fact that if a project has no open issues the Agile is not available at all, and so the feature to create new tasks from it is not available.