minimserver 2.2-7001 sees only the first subfolder I installed under Music folder

[simoncn]

This sounds like a folder permissions problem. On DSM 6.x and earlier, MinimServer runs under the root user and has access to all folders. On DSM 7.x, DSM runs MinimServer under a special user named MinimServer and this user needs to have permission to access your library folders.

The simplest way to do this is to give all your library folders read permission for the administrators group. The MinimServer user is a member of this group, so MinimServer will be able to access these folders.