I just recently again got into the position that a model needed to be adjusted and fixed and while DM has a great deal of self healing it is not flawless and magical
so you switch from solid to patch mode but the extend surface only goes sofar.
an untrim tool is so important to have when working with imported STEP data that needs to be adjusted or improved - even for a software like Fusion.
I needed to send again the STEP model to Rhino to fix an issue Fusion was not able to and that is a little embrassing