Nexus3: move a specific Maven repository into an another blob store

Currently this is not possible. You would need to recreate the repository with a different blob store. We have some future plans for supporting something like this, but that's a bit off. Pop over to https://issues.sonatype.org/browse/NEXUS and file an issue if you would, it will help raise awareness of your need :)

I think it's also noteworthy that when you upgrade, you can select what blobstore you want the upgraded repos to fall in as documented here; specifically 'Repository Defaults' section 'Destination' field.

So, for people who haven't upgraded yet or who are willing to rerun (basically scrap and start over) the upgrade, it is possible to get things organized as you want before hand. First, you can first create the blobstores you want things to be organized in and then during the upgrade process select where you want things to go.

UPDATE: As shown in NEXUS-12016, this is now possible for Professional (licensed) instances (for hosted repositories) as of 3.28.0.