Simply, create custom bags. Example; First bag I want is a big 39 slot bag. I put all my equipment stuff there. I create a new bag, which is 10 slots, for flasks and reagents. Next bag I create is for random stuff, it's basically the bag slots i have left. They would be all empty or with the stuff already from the bags, and you had to sort it out yourself where you want your items.
And of course it would work like it picks the first slots of the first bag, say the first 20 slot bag, then it adds 19 from the second bag and so on so the sorting won't get messed up.
No automation, nothing like that. Just simple, create bags of the size you want. Nothing more, nothing less.
I've been searching a lot but cannot find this addon. Could anyone please help me build one, do it yourself, or please find another solution that could work somewhat the same? Can it even be done?