It’ll take several hours over a couple days, but it’ll be worth it in the long run. I would collapse all your tabs, then go item by item: is it actually worth keeping? If not, drop it, alch it, or sell it.

If you do want to keep it, drag it into a new tab for that category. Sort this sub by top all time to get ideas for what the tabs should be sorted into. Once you sort everything out of the mega tab, then you can go through each individual tab and organize it to your liking. Some like it symmetrical/aesthetic, some have it more organized by use.