From Release 2019b you can disengage joints. So you can "glue" together two solid with a Weld Joint, and then during simulation you can disengage it using a signal switching from 0 to -1, and the joint becomes a 6 DoF joints. This would mimick "slicing" a solid in two, with the two solids disengaging. I'm attaching one example (for 2020a release).
hope this helps