I've used Firefox for years on my iMac with its 5K display. The UI was fine. Today I had to delete and then re-install Firefox because the program had started crashing repeatedly. I lost a lot of bookmarks & tabs. Upon opening the new install, I saw that Firefox now shows a miniaturized UI that is very difficult to read. I refer to the UI elements (tabs, bookmarks bar, URL/search field), not the web pages themselves. As part of the installation, I went through all the settings, and I didn't see any controls for the sizes of UI elements. So I searched the internet and found many reports of similar problems over many years. I tried a few suggested changes to about:config settings. Nothing has worked. I am exasperated. What am I missing? Can anyone help?