If you aren’t installing via package manager you could manually separate by the same process.
C:\Users\yourUserNameHere\AppData\Roaming\McNeel\Rhinoceros\packages
in this folder you will see subfolders for 7.0 & 8.0.
To add a Rhino 8 only GH plugin, in this example Sunglasses. I created a Sunglasses folder in the 8.0 directory, added a manifest.txt with the folder name 8_only (name this whatever you want), which houses the .gha file.
