And it also got rid of the share function. I'm seriously considering not using it as a browser anymore because of that.

If this is a result of the updates that installed themselves yesterday I expect we will all have our own dislikes. Who does a good browser? I have a strong dislike for the big names.

Hi,

Starting in Firefox 89, Compact Mode is no longer supported. If you've been using Compact Mode on a previous version, you should be able to retain the feature. However, for the best experience, we encourage you to use the default Density setting.

If you are an advanced user, it's still possible to activate it in the Configuration Editor (about:config page).

1. Type about:config in the address bar and press Return. A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
2. Find the browser.compactmode.show preference.
3. Switch the toggle to true and then close the tab.
4. Click on the menu button The image "fx89menuButton" does not exist. to open the menu panel.
5. Click More Tools menu.
6. Choose Customize Toolbar.
7. At the bottom of the panel, click the Density button.
8. Choose Compact (not supported) from the menu options.
9. Click Done.

More about that: Compact mode workaround in Firefox

Thanks Seburo, I followed your detailed instructions and the toolbars are now not so high. I would never have found this procedure without help, just a shame it was necessary to do it. The Firefox text, eg list of Bookmarks, are still of larger line spacing than before but this is not so much of a disadvantage as the loss of web page size caused by the larger toolbars.

"However, for the best experience, we encourage you to use the default Density setting."

This is basically Firefox saying they don't care about user's personal customization. But if you still really want to tweak stuff, go through this warning page that many might not be familiar with and fiddle around with it.

It's like going to a shoe store and you're looking for a size 8 shoes. The store owner instead is like nope for best experience, we suggest you use this size 10 shoes that the company is rolling out. It's more modern and easy on your feet with lots of space so you'll definitely feel comfortable.