@crankygoat Part of the original problem was the obnoxious "picture-in-a-picture" function which was added without notice to me nor any consent from me. That was uncovered while I was chasing around modifying other things and has not recurred. The key part of the solutions presented here which appears to have worked was the set of changes indicated by @cor-el who mentioned that my Firefox had been set to "Private Browsing" mode with me having not understood the uselessness of that permanent private browsing mode. I made those changes as indicated 1/14/20 at 7:17pm. As for the /doomed or /entries folders, my Windows 7 search says I have neither such folders. At no time was this a cookies problem (which were being cleared) but always site data failing to get cleared from the cache where it was being retained. It is in fact the site data which absolutely must be cleared out of the cache for anything else to function. In any event as of today January 18 I am no longer able to replicate the accumulation of garbage NOT going away when I exit Firefox, do nothing for awhile, and then bring up a new incidence which is *now* always showing something in the range of 26.0 to 28.0 Kb upon startup. I'm going to treat the problem as SOLVED because of that set of corrections in my settings and can only hope that any future "updates" refrain from modifying any aspect of my settings.