When there are more the 25 groups how you select them gets harder! 

The window is reduced from 6 to 4 groups at a time and it means there is more scrolling up/down to find the ones needed.  List them all, don't restrict the view.

But the most disappointing aspect is that the ease of the checkbox method is changed to something that is more difficult, the user needs to hold the Ctrl key down to select more than one which is very much prone to the user accidently removing any other secondary groups the member may have as they cant see what is currently selected.

Please change this to something more user friendly.

 

 

There is a working solution already when selecting groups in Commerce > Store > Store Settings.  Its the same number groups as my screenshot above.  Can you do the same when selecting members secondary groups?

I'm surprised this isn't getting more attention. 

It would be great if get an option like the multi select from select2 https://select2.org/getting-started/basic-usage#multi-select-boxes-pillbox

This way you can instantly see, search and edit the secondary group for a user. 

Wow, that's a nice selector.

It sure is, we use it a lot for our own platform and it helps with readability and seriously is a quality of life improvement for selections like this.