A way to edit this list would be handy. The only way to remove an item from the list from within Sonar is to delete or move the project folder, then select the project from the list. Sonar will then report an error and remove the project from the list.
Yes, I realize this is small in the grand scheme. I'm putting it here so it can be documented and maybe addressed when somebody is doing other work nearby anyway
UPDATE: As the above process crashes Sonar, it is a big deal after all.