Judging from this thread:
the shrink and stretch part of this request should probably include “auto shift clips on the right” option. Possibly depending on the status of the “auto shift” button (?). Currently, inserting a shorter file in a clip shrinks the clip but does not auto shift clips on the right. For this part of the request (not my original unchanging “locked” clip request, which I still need, and don’t want auto shift on) auto shift would be needed for both shorter and longer replacements if it was desired to shrink or stretch the clip.