Root folder is the folder where FontBase stores all the fonts it's working with. On first installation FontBase will create a Root folder to store the copies of font files added into it. The location of the Root folder can be changed via the "Root folder" section on the Settings page.
You can set the path to your pre-existing main font folder as the Root folder. However, please be aware that in this case should you decide to delete some fonts via FontBase these fonts will be deleted from the Root folder too, so if your only copy of a font file is in the Root folder, you will permanently lose it. That's why we recommend keeping the Root folder separate from your main font file folder, as a measure of precaution. After all, better safe than sorry.
When you're uninstalling FontBase, the Root folder will stay and can be easily deleted if needed. After any subsequent installations FontBase will remember the last Root folder path indicated in the Settings page, be that the default path or the one you've seleced manually. Unless you completely wipe all FontBase data, including the settings data, then the next time FontBase is installed the default Root folder path will be used.
The default Root folder path is:
Windows: "C:\Users\(YourUserName)\FontBase"
MacOS: "\Users\(YourUserName)\FontBase"
Linux: "\Users\(YourUserName)\FontBase"
Please keep in mind that your system fonts are always active by default, FontBase cannot deactivate them. Trying to activate them via FontBase might cause font bugs while you're using your computer. Nothing a reboot wouldn't fix, but could still be annoying. For this reason we highly recommend not setting your Root folder location to your system font folder and not adding the system font folder into FontBase.