I was fed up with copying one solid part so I could subtract it from another without losing the original. So I went to work using AutoLISP/Visual LISP and in a couple of days I came up with STRIM, The 3DSolids trimming App you can now download from Autodesk Exchange. Using it you can select a bunch of "trimming" solids whose volume will be subtracted from another bunch of solids selected to be trimmed. They say "time is money" and this tool I'm sharing with you all has sure saved me a lot of time. The new version of STRIM incorporates a "select All" option which goes a step further in streamlining your workflow.
Once I solved the trimming, I wondered if sometimes I would need not to TRIM the solids, but instead to SPLIT them in a way that all the portions overlapping would be split into separate solids.
So I put AutoLISP to work again. And here came SSPLIT, the other App I'm sharing.
These two tools are now packed into a single Application: TRIMSPLIT, available for downloading at the the AutoCAD Exchange Apps website.
But I don't want to keep the way it's done secret. I've been a teacher all my life and that's a thing I really enjoy. So if you wish to do things like this all by yourself, then my book "AutoCAD Expert's Visual LISP" can help you. Be it in the Paperback edition or the Kindle e-books.