both umc.widgets.MultiSelect and umc.widgets.MultiObjectSelect aren't disableable.
*** Bug 35529 has been marked as a duplicate of this bug. ***
*** Bug 35553 has been marked as a duplicate of this bug. ***
For UCS 4.0 I disabled the add and remove button, the grid still has no dark background. → so it blocks the functionality
Created attachment 9041 [details] patch Grey out the MultiSelect widget and make it not clickable
Can you attach a screenshot of how it looks?
Created attachment 9046 [details] iamge disabled=false / disabled=true comparison