There was an existing entry for a 2002 album (Kokomo) which is a actually a Japanese remaster of a 1982 album. I created a release group and a release for the 1982 album, but I can’t see how to move the 2002 album to my new release group.
You need to go to the page of the release you want to move between release groups, then go to “Edit” tab. Then click on the magnifying glass icon in the “Release group” text field. This will pull down a menu where you can search and select release group to move to.
If it’s too difficult to find the correct release group in that search box (e.g. because there are too many with similar names), pasting the MBID of the target release group in the text area should also work.
As a side note. I’m not familiar with this Kokomo band, but is seems strange that there should be so many release groups with the same name. Is there a reason to keep these release groups separate?