You need drawer and shelf organizers and baskets. You have plenty of storage already for 2 people, and a very nice bathroom!! Do a pretty runner on the floor that goes the width of the vanity instead of the two mats. You can put extra padding under it. I have a plastic container with my “day” face products and one with my “night” face products. I grab the container out, do my thing, then stash it back away. I decant my face cleanser and hand soap in pretty pump decanters that stay on the counter. Toothpaste and toothbrush in a tall tumbler that matches the decanters. Makeup is organized in drawers. Cotton balls, q tips, hair styling tools and products etc in drawer and shelf organizers. If the lower doors open to cavernous spaces, invest in a system that is easy to pull out and use, which will help you stay organized. I try to keep my products grouped in containers by use, which helps keep the drawers and shelves clean. Containers get washed as needed, but it’s much easier than removing a whole shelf of stuff. I am RUTHLESS about throwing out products I don’t use often.

It looks like it was added at some point. And it extends into a space behind it. What do you want to store? I’d think another built-in with drawers below and a cabinet with shelves above would provide good storage for bathroom items.

I like the functionality of the one below but this link offers many other options: https://www.pinterest.ca/pin/413627547021201672/ (I did a search google for built-in in bathrooms):

I would put a tray across the tub for toiletries. A couple hooks/shelf or a towel bar on window wall centered on the tub. And a stylish poof/stool with a tall plant in the corner to the left of the tub. Skip a cabinet/other storage there.