There are two types of VSE packages (not counting hotfixes).
You can check in Full installs to the Eval, Current, and Previous branches
You can do the same with the patches
Previous, Eval, and Current are just labels. You can check in a lower revision patch to the Eval branch, or the current branch, or the previous branch, So you can check Patch 9 in to Previous, Patch 8 into Current, and Patch 7 into Eval. It doesn't really matter as long as you match your Agent Repository settings as well.
I think maybe I was not totally clear, I know I can use those branches in any way, but they are designed for that specific reason (and I wish to keep in that way), otherwise that means I need to change the way our entire team uses it, specially because I´m not the only one to handle with ePO and VSE, I can´t take any chances of our Support staff being mislead because I changed something.
I want to create a legacy VSE entry on Repository just to have better control between product versions, in the same way you can with older major versions, but I dont know if it is possible
As far as I know, you only have the 3 branches. Previous, Current, Eval.
You can use them any way you wish, but that's the limit.
Full package deployments for Previous, Current, Eval do not need to match the patch branch. So you can have Full deployment package VSE 8.8 patch 8 in the Eval branch, and you can have VSE patch 8 (upgrade patch only) in the Current branch.
But if you're looking to make a 4th branch for the repository, I don't think that's possible.