I like to separate my bars into Action vs Bonus Action as well as separate spells based on their spell level so I can keep better track of what I have, what is left, what actions are available.

I also collect pouches and backpacks to place objects in. My first pouch is healing and helpful potions. My second pouch is throwables, dipping materials, and arrows (anything to harm someone in combat). My third pouch is for scrolls on the characters that carry/use scrolls. I also put my shovel and anything else I want to have on me but want to accidentally sell it within a pouch. I then place the pouches on my hotbar on the far right instead of the individual objects (except for shovel). So during combat I know if I need to take a potion, it's in the top bag, harmful items in the middle bag and scrolls in the bottom bag.

I have my bars extended to 3 vertical slots.

Re: skills and spells not falling off, I unfortunately do not have a solution.

For casters, I tried to keep concentration and non-concentration spells on different rows. And I try to keep abilities that recharge on a short rest on the left side of the bar to encourage me to use them