Alright, so I deleted PSO2 windows version, a month ago. I'm now downloading the steam version which, is going to take about 6 hours. How can I accomplish this without the need to to download the Xbox windows version again.
You can't link them without the MS store/Xbox version because you need to issue an account linking code on the MS store/Xbox client.
https://pso2.com/news/announcements/steamlinkaccounts
Your other choice for a single install would be using the Tweaker that allows you to switch between the 2 versions.
So, since the steam version is downloaded. I can use PSO2 tweaker to switch versions and log into my Xbox account on it get the code. Then, switch it back to the steam version?
Eh, not quite sure how it going to work if you installed the steam version from the steam store - the Tweaker installs its own version of the game that can link to both MS Store and Steam. I mean you can use Tweaker to run the MS Store version but that's downloading and installing the game again.
People had to completely remove the MS Store version to do a clean Tweaker install when they had issues with MS Store.