Is there a feature to 'plug' geometry on surfaces?

 From:  Frenchy Pilou (PILOU)
9778.5 
PS Instance function for mutual modify (without the Mirror above) is a little tricky!

Draw Object A (here on the left)
Copy Move it as Object B
Select Object B !!!
Enable History !!!
Modify object A !!! ;)

EDITED: 26 Apr 2020 by PILOU