you mean add a shape to an already group of shapes
If yes
- for group, go to behavior and set "accept shape on drop"
- for shape, go to behavior and set "add to group on drop"
Now when you move shape on top of group handles, it will add it to group
can right click group and shape to get to behavior UI
Last resort, turn on developer mode File ==> option ==> bottom of the UI ==> select enable developer mode
Behavior is there as well.