The new version of the steam mobile app is vastly different than the previous version. There are a couple of new features that are supposed to make it easier to sign in on steam without having to enter a steam guard code
The app allows you to view your entire game library in a grid-like format, showing game covers and titles that you can sort through with the included filters. You can remotely download and update games on your PC.
There is a new store browsing experience for mobile screens, as well as a way to search for and purchase games, complete with the community and news items you're used to in the desktop version.
It is possible to use aQR code to log in to the steam deck.
You don't have to enter your password or steam guard code when you use the update to get into your account. When you sign in with a QR code, the app will show you a confirmation page with a map and location information. You can verify that you are the person who signed into your account from here.
If you don't want to use your camera to sign in, you can confirm it with an "approve" or "deny" prompt. This will allow you to skip entering a steam guard code, but you will still have to enter your password and usernames. If you leave your account on someone else's PC, the app will show a list of authorized devices, which you can use to sign out of Steam.
The alpha version of the app was released in August. It's a welcome change for someone who can't keep track of their password or steam guard codes. The chat app will be updated with various bug fixes soon to follow, and it is also working on bringing its newQR code sign-in to the steam deck.