Basically- The goal is to have two tabs. On the left would be the bases file and on the right would be whichever file I click from the bases view. This is not opening a new tab to the right (like with middle click or Ctrl+Alt+click as that constantly adds new tabs.)
This is so you can click on a file in bases and it overtakes the right tab and shows that file (like a dual pane file manager.)
Things I have tried
You name it- searched and did the hotkeys, etc. but found nothing useful for my precise use case.
Does showing the base in a sidebar (instead of in a main workspace tab) suit your workflow and landscape? From there, base links work the way you described: they open in the active tab, without creating a new tab.
Oh wow- I have never dragged anything to a sidebar before. I was looking at the far left dock and there was no option to display the base by itself but you can drag it and boom, there it is.