Ideally this would be with the use of the flag in the DM settings for “Form Extended Structures” but there is a bug ticket in right now for this not working correctly. It functions, but you can only destroy the first DM placed in the scene or the first one that another DM is in contact with. So for instance, if you placed a box DM and a sphere DM in contact, they would stay connected even if another chunk was broken free that allowed them to stay connected, however, the bug right now doesn’t allow any damage to be taken by the second one (sphere) that is in contact until the first is destroyed or it’s completely broken free.
I hope that makes sense, probably confusing though just trying to describe it, but that would be the easy method to use if the flag worked properly right now. IIRC this is backlogged at the moment, so I’m not sure when it would actually be fixed. Sorry.