Don't remove it, you'll lose your data.

The places.sqlite file stores bookmarks and history. If this file is over the default of 5MB then this indicates that you have a lot of history stored in Firefox. You can remove unwanted history and click "Verify Integrity" on the "Help -> More Troubleshooting Information" (about:support) page to perform a vacuum action on places.sqlite.

The webappsstore.sqlite file stores some persistent data stored by websites, so you lose this data if you rename/remove this file.

Thank you so much. Please excuse my lack of experience and ability to solve this for myself.

From your answer, webappsstore.sqlite needs to go, if safe, as that which web sites have stored is exactly what I want to get rid of. Could you kindly tell me how to delete it? (If it is a matter of opening my profile and just deleting that file from inside Windows, I can do that. (Not that you need a bio of my (in)abilities, but I can make my way around and function in file management in Windows relatively well but have done NO editing inside profile; I can learn/research. :) (I do know how to look at profile and the command about:config. Thereafter, not so much. (embarrassing!)

Re: places.sqlite I clicked on “Verify Integrity” per your suggestion but unsure about the results. Attached is a ss of a portion of that result. History is not a high priority for me, especially keeping more than I need/too much.

All that I really do not want to “mess with” are my personalizations and overall settings, including appearance, security, size of icons, toolbars, etc. Otherwise, I just don’t want to screw anything up.

Many thanks, once again!