I haven't tried to create my own plugin before and have created Grails applications successfully but not recently so this may apply to any "New Grails Domain Class".
In summary while IDEA goes through the motions and does correctly create the class.goovy files they are not visible in the IDEA Grails View nor Project View.
I ran the New Project to create the plugin, using Grails 2.1.1, it seems to work correctly
I then created a domain class, this also appeared to work correctly and says it creates the .groovy file in the console log but nothing is displayed in the Grails View nor Project View (Left hand panes). After this first failure I checked in the actual files and there is a correct, blank domain class file there. I then created a second class and while it seemed to accept the entry it didn't show anything on the Console log after a few lines. I left it for a few minutes and repeated the same New Grails Domain Class, using the same name, and it worked, well it went through the motions and said it had created it but again nothing shows on the IDEA views. However as before the files are there. Interestingly the test files which are created during the create domain class process are both visible in the Views
I closed IDEA and reloaded it but still no class showing.
I did note this problem with package names a few months ago (although no one responded) http://devnet.jetbrains.net/message/5461667#5461667
Of course now Grails does insert a package statement at the start of the domain class.
The files were created in a directory ../domain/pckgname so I copied them up one level and removed the 'package' statment' still IDEA could not find them.
I then went back into IDEA and went through the New Grails Domain Class and attempted to re-create one of the existing classes. Correctly it said it "...already exists, do you want to overwrite ?" I replied "No" and then suddenly all of the classes (the original pair and the pair I had copied) were shown.
I then created a completely new Grails Domain Class and it immediatley appeared as it should and presented itself in the right hand pane to be edited (the previous missing ones had not so done when they were created.
This is IDEA 11.1.4 (but I believe the same happens with 11.1.3 - I did a quick test when I first noticed the the problem) on Xubuntu 12.10, Grails 2.1.1.
I have to say that like the previous problem I noted it is rather irritating and has wasted a good few hours of my time.
I would welcome some comments