Hello if I understood correctly, here is what you should do:
1: Create a sketch with a material removal function in your room. ( makes the shape more or less as it should be )
2: go back to your assembly and click on the part (the one in blue)
3: Then made editing of parts
Thank you for your answer, I've already used this technique, but given the shape of the part (yes part in this case, not an assembly), it's complicated, because the base is a form of revolution with a shape.curve.
It would be necessary to be able to start from the curved surface of the revolution to a vertical extrusion direction.
You can sketch the two bodies and then use the split function to separate them. Then make your sketch and then do your material removal by selecting "up to the body";)
The feature can also be used in an assembly in the Assembly Feature topic.
Alas, I tried the technique with the surface as the end of extrusion, but without success, the error: "Rebuilding error: The planned material removal does not cross the model. Please check the sketch and direction"
Having tried with 2-3 different combinations, still no success... Look at the shape that the extrusion has to come to, maybe it comes from there?
I think it would be better to keep the vertical "cylindrical" part as an unfused body until the removal of material (only on this independent body). Then use the combine function to merge the 2 parts of the room.
You go back up your tree before the revolution that creates the matter you want to remove.
At this point the surface on which you want to stop your removal of matter must exist.
You select your surface and make a sewn surface function -> SW creates a surface for you.
You go back down to the bottom of your tree and you remove material to the sewn surface you just created, it should work (the material removal sketch must be totally contained in the surface).
(but I just realized that we may have already communicated on the same subject here or elsewhere in view of the last link I gave since it's the same Heuyman username on the other hand I still have the same username)... ;-)