How would you change the Steam Interface?

Make it less reliant on Chromium. There's no good reason my library page should use nearly 1gb ram when it had nearly 0 footprint before moving it to Chromium.
And if they roll another chromium-based memory leak into the release? Fuck sake. I spent months only able to run Steam with Chromium disabled, something that's no longer an option.
- And it's extremely glitchy on Wayland with an Nvidia GPU, even with hardware based accel disabled. I moved from Spotify to spotify-tui and from Discord to a dedicated FF instance with canary.discord.com opened by default. It has a smaller memory footprint, that's just sad. And of course it works much better.
  Steam is the last thing requiring electron/chromium.

They should focus on performance over UI changes. It takes 20s to open on my fast gaming laptop. That's not far off from EGS and Windows itself. Meanwhile, the electron-based open source Heroic launcher takes 3s to open.

Get a consistent style, that mf is more inconsistent than windows.
Consolidate some items, a lot of them are duplicated
- I find it annoying when it suggests me games that are already on my Wishlist.

If it's gonna use a load of memory let me theme it, colour schemes, skins based on games and let me switch off the community feeds that are full of shitty trying to be funny guides and crap.
Custom toast popups that pair with the game you are playing.
Reminders for the free stickers in the mobile app during events?

Basically everything in this video: https://youtu.be/cDY2p1CTkPo?si=PxNMLURX7MMx6dLG
Seriously it's mad impressive
- I agree with 100% of this but the only other thing I would add is the option to have trailers be played when clicking a game in my library. Since I have so many games from sales and what not that I need to be sold to play a game I already own or have a filter showing all purchased games in a grid that I can browse through. having to click on the game go to info and then going to view store page is a chore.
- I actually watched this video a few days ago and it's an amazing new look. Wish they would get hired by Value to design the whole system as it's impressive.

Others already mentioned the more important ones, like less chromium and especiallt better performance jesus christ...
Id want a skin like the 'steam compact' one we had years ago, if you wont add skin support then pls add smaller UI as an option for low-res and Deck desktop users

Fix the hover drop downs (from library or store buttons at the top) to not appear over other apps.
I think this is a Linux only issue but when I’m not even tabbed into the steam launcher and accidentally move my mouse over one of those buttons at the top it shows the dropdown over my currently focused app :/
- Haven't seen this bug myself, so might be a Linux only issue.
  
  This is what it looks like

I honestly want to be able to use similar plugins or an equivalent from my steam deck. The two j can think of are the HLTB (how long to beat) and the protonDB badges. When I look at my library on desktop I can't see if it's deck compatible unless I'm just missing something.

Accessing chats in big picture mode seems worse than how it worked in old big picture mode. Usually if you are in big picture mode it is because you are using a controller, and with the new one it is hard to navigate chats with the controller so I end up using a mouse.
Also, would be nice to have an option to display the entire text of a comment in pop ups, since it often cuts off and I have to entire toggle to overlay , alt tab, or look at the terrible steam chat mobile app. Apps needs work for basic messaging with it not refreshing to show the most recent chat consistently so having to exit and reopen.

Just make it consistent. There are so many buttons, etc. with different styles, layouts, etc.
- Yeah it's one of the major downsides for new users as it will confuse those that are moving from console to PC.

I wish 'exclude by tags' was more accessible, maybe if it prompted you to view that setting after you 'not interested' a few games that shared the same tags.

I'd remove the need to authenticate for accessing things that are already on your computer. Why does it have a "remember me" checkbox if it's not going to remember me...