[PeterK]

It still seems to work if you first rename the directory, use a project icon and set up the default tool, save it and ...
(then change its type to drawer and save again. Change the type back to project, save it and ...)
... finally restore the directory name to the same as the icon name.

Did you try that already?

As long as a directory exists which has the same name as a project or tool icon they will be converted into drawer icons automatically.

Changing the type to drawer and saving is only done for creating the drawer data entry for the icon, but maybe not required.