Thanks again, Ken!
Here is a screenshot of part of the top of my screen. It is the size of the icons in the rows below the menu row that grew much larger. I've guessed that they must be at least twice as large as before, almost as if I changed my Windows settings for the number of pixels across the display.
Fx103 icons.PNG
The link you posted I followed and read as related to the size of lines in drop down menus, which is not my issue.
Perhaps I misunderstood. I can see that I didn't make my point well.
FWIW: I have a question in to Mozilla Support for Firefox. I shall post here if I get a solution or am told that there is none.
![ThankYou :thankyou:](./images/smilies/thankyou.gif)
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