Unfortunately, I do not have a Mac for comparison, but please check for either "Preferences" or "Settings" on the main menu accessed using the 3-bar button at the right end of the main toolbar. Does it exist there?

If push comes to shove, you can type or paste about:preferences in Firefox's address bar and press Return to load the Preferences page by that internal address.

Any luck?

P.S. This forum doesn't accept email replies, so please follow up in your question at https://support.mozilla.org/questions/1419624

Thank you for your attempted answer, but a solution based on a pc isn't helpful when the problem is occurring on an Imac.

Did you try this:

If push comes to shove, you can type or paste about:preferences in Firefox's address bar and press Return to load the Preferences page by that internal address.

Thank you for your attempted answer, but a solution based on a pc isn't helpful when the problem is occurring on an Imac.

His reply was not just for Windows but also for Linux and macOS as "Preferences" or "Settings" was mentioned.

from https://support.mozilla.org/en-US/kb/firefox-options-preferences-and-settings (if I change article to be for Mac on right).

This article summarizes the Firefox Settings panels and what types of settings they contain. In the Menu bar at the top of the screen, click Firefox and select Preferences.

Could have sworn it was changed to Settings for Windows, Linux and macOS however the article says it is still Firefox > Preferences for for macOS. It used to be Tools>Options for Windows and Edit>Preferences for Linux.