DB is programmed to put items in the 1st and 4th stash tabs. Gems, mats, tokens go in the 4th & everything else in the 1st. AFAIK no known way to configure it to your llking
Where is this mentioned? In the past, I had gems in the 4th and they'd get stashed in the 1st. I moved them to the 3rd and that worked for a few weeks, then stopped.
I've moved gems to literally every tab and the bot pays no attention to where the stacks are and drops the recently looted ones into whatever tab has open slots.