I don't know if it was on this particular forum that I previously posted, but I did post a question yesterday about why the app icons no longer appeared on my toolbar, and how I could restore them. Someone from Firefox responded, but he didn't provide an answer for me.....at least not immediately. In the meantime I contacted the support team for one of the apps (Bitwarden, to be specific), and they were able to provide the solution. I informed the Firefox person who contacted me that a solution had been found, and he asked me to post that solution here, since I was not the only one posting such a question yesterday. If your app icons disappear from your browser toolbar, then the solution is to create a new profile for your Firefox account, because the old one has apparently been corrupted. As soon as I created that new profile, all my previous app icons immediately appeared on the browser toolbar, with no further actions required by me. I hope this information will help some of you. It is possible, I guess, that other browser problems incurred might also be resolved by creating a new profile.