This is now much easier with virtual mappings introduced by 1.14.0 Beta (recently updated to 1.14.1)
Having used 1.14 for a bit now, I’ve adopted a practice of using a line or two to set up all my “modified mappings” and ending those lines with a Virtual (say H) which I reserve solely as a “mapping source”.
(Often this Virtual will not appear as a Virtual-IN , which simplifies things massively elsewhere (No need for Filters as in “message event” pipelines.))
I’d assume your suggestion would involve adding an In|Out Low|High ranges (much like Remap/Rescale) in the Add/Edit dialog box. Would values outside the In Range be clipped (cf Rescale) or discarded (cf Remap)?
PS. Your other recent requests have got similar topics elsewhere. I’ll add links to them if & when…