No, this is not possible.

Edit: of course 'everything' is possible, as this is software, but not in any way I can see would be meaningful (or wouldn't take quite some effort and time).

The action server accepts JointTrajectory goals. Polyscope does not generate those. The UI of Polyscope sends URScript statements over the primary interface to the URControl daemon running on the robot / on your computer (in the case of ursim). You'd have to get 'in between' these two, capture the statements, convert them to JointTrajectory goals and send them to the action server. But this is only part of the problem, as you now have two separate robots (one in Gazebo, one in ursim) that are not in-sync.

What I believe you're actually asking for however is a jogging interface. You could see whether jog_arm suffices.