There are 2 separate issues in this thread. The OP's complaint about CMD-V not working as desired appears to be a Qt bug (or new behaviour), apparently not fixed in the latest release.
The issue raised by Turtle91 is a "missing feature" in Sigil. The Clips window was designed to paste into the editing tabs, not the F&R box. You are meant to use Saved Searches for F&R, but who says you can't use things in whatever way works
The easiest workaround is to use the Clip Bar - then you can single click a button to paste into F&R.
Changing the code so that the Clips window also works for F&R is easy enough now that it's been suggested.