This is a situation where it may be smart to just download and install over the top of the current release. Unfortunately, the latest release is 128. I suggest you click help>about to verify your version number, which will be 115 if you keep it current. Then, go to

https://ftp.mozilla.org/pub/thunderbird/releases/115.12.2/win64/en-US/  and download current 115 version That link assumes you are USA resident and speak English). If not, click the 'Dir ..' above the exe download to revert to prior page in FTP.

This solved the block delete problem, and I finally found the option to turn off double spacing when editing a message. Thank you. Still have the issue of limiting the length of a line in a message, including when reading your response - I have to scroll across to the right to see the whole line in your message, and when editing a new message, the text goes on to the end of the screen display, and then some. Any suggestions? Thanks again for your help.

I'm glad you're having partial success. I am puzzled on wordwrap as I have it and have done nothing. There is an addon, 'toggle line wrap', but it shouldn't be needed (and may not work), but I offer as a possibility.

Did you make a change to mailnews.wraplength ?

No - I just reinstalled per your instructions. In addition, the folder list and email message list are now double spaced. I have no idea why. I have a lot of folders and email messages, and would prefer to have a compact list. Thanks again.

Can you post a screenshot of that?

Apparently not. When I use "Print screen", I can paste the result into a document, but cannot paste it in here. Any suggestions? Thanks. Tried the "Add Images" button, but that failed.

Click the hamburger menu and select 'density and set to 'compact' and see if that addresses the issue.

Good morning, David. Thank you. Solved the density problem. Still have the issue with the data in a message where I have to scroll to the right many pages to see the whole message, or it occurs when typing a message.