Mamp-PRO 6.x on Mac Catalina can't access the folder with my websites anymore

I upgraded from Mamp-PRO 5 to 6 and now all the websites are red.

In the «document root» field, it says «restricted folder» and when I try to add a new host, I can't select a folder - they're all greyed out.

My files are located in /myUser/Library/Webserver/Documents/…

I gave apachectl, httpd and Mamp-Pro full disk access in the system preferences.

Any idea if I can fix this without moving the whole folder to a different location?

The exisiting websites are working, though (e.g. I can start Apache and the local websites are responding).

(running MacOS Catalina)

It's possible that changing the name of htdocs to localhost will do the trick. However, here are the steps I took to correct the problem:

• Stopped MAMP Pro servers
• Copied Applications/MAMP/htdocs to my Dropbox folder (I'm guessing it could go in the documents folder or anywhere else)
• Clicked on localhost in MAMP and chose the new document root location (Dropbox/htdocs in my case)
• Chose new document roots for all my hosts at the new location

Of note, MAMP automatically changed the name of htdocs to localhost. This is the basis for my assertion at the beginning of this post.