At this time (version 18.104.22.168) the way we can edit an "Assign" widget is better but could be improved:
We can delete the line "Variable" or "Value" with a shortcut (SHIFT + DEL), but we have to do it for both lines. My Idea has 2 points:
1. When clicking the "down arrow" (see image) we should see at the end an option called "Delete Variable" or "Delete Value"
2. When we make "Delete Variable" (either with the shortcut SHIFT+DEL or by using my option 1 click) both the "Variable" and "Value" lines should be deleted.
a) if we make delete on the left side of the assignment ("Variable") that assignment should be deleted ("Variable" + "Value").
b) if we do it just on the right side of the assignment ("Value") only the value would be deleted.