There are several layouts, and you were not specific. Could you post a screenshot of what you see? That will help. Thanks, much.

the vertical divider between the email messages and the various folders, on the left, is slideable but the horizontal divider between the various emails, and the one being read / answered can only be slid halfway up, and that oversized horizontal divider in the middle, (gray and yellow), with from/to/subject/reply, etc., is just in the way and nothing can be done to minimize it... it is WAY TOO much WASTED space, and should be up at the very top somewhere, where there is space in the main header menu. thanks

And under the Subject header, where there is a dark black > before the subject of each email, that indicates that the message contains more than one message, in a thread of conversation; but I want to turn that off, because sometimes I can't find the email that comes in, and sometimes more than one person answers a group email, then only the first person's name is shown, and every other person that answers or comments gets dumped down into that hidden thread until you click on the >, and I wish there was a way to turn it off. I've spent hours looking, and though I find something that sounds like a choice to turn threads off (wherever I found it), it does not do it. Thanks, Robert

The minimum height of the threads pane can be adjusted:

https://support.mozilla.org/en-US/questions/1427439

The size of the Header Pane can be reduced with Compact Headers.

Set View/Sort by to Unthreaded. Press Alt if the Menu Bar with View is hidden.

Thank you. I don't have time to play with it right now... but will copy and save your reply, and try it when I have time, and will repost here, thanks. Any idea about the turning off of combining email threads together? Thanks, Robert

Setting the view to Unthreaded should turn off combining emails. If you mean to turn off combining messages from multiple accounts, set View/Folders to All only.

Hi, I don't see "unthreaded" anywhere under VIEW. There is a sub-window called threads but no "unthreaded" option thanks, Robert

click view>sort by

thank you!