Add/Remove multiple and Edit Members dialog filter control

[Robert Crawley]

Hello all. I hope I am posting this in the correct location.

I need to find a way to provide a default filter on the Edit Members dialog when someone selects the "Add/Remove multiple" button found on a list field. 

I have one set up on Task that is referencing sys_user_grmember with a simple filter of user.active is true. The dependent field is set to assignment_group. I also added an attribute for ref_qual_elements=assignment_group. Though, I'm wondering if this is redundant with the dependent field or I'm simply not using it correctly.

I added a list control so that the user record's Name is shown instead of the sys_id. 

Everything works as expected when doing a lookup from the "Select Target Record" option, or using the search feature. I only see those active members from the currently selected assignment group.

The issue comes in when the "Add/Remove multiple" button is selected. The edit members page opens with an unfiltered list. I have been searching for a few days and haven't found anything that relates to this particular use case. I've found several discussions on how to handle this from an "Edit..." button, but that doesn't really work for this situation. I don't see an actual UI action that appears to be tied to this button or field. I've gone into the dev tools and found the element is triggered from <button onclick="editList('rm_story','sys_user_grmember.do','rm_story.u_resources','sys_user_grmember','false','Available Users','Selected Users') ...

Which, looks like it's passing values in for the dialog, but I haven't been able to locate this particular script anywhere. Is it even possible to manipulate this functionality or am I starting to slip into the DOM manipulation area?