How do you remove apps from the app library?

What apps are you trying to remove? Some of the built in apps can’t be removed. And there is at least one (Robokiller) that “lives” on the app provider’s server, so if you delete it from the phone that does not remove its function from your account. Check with the provider’s website for how to remove them.

The app may also have a profile that you had to install. If that is the case see this→How to delete an app that has a configuration profile on your iPhone, iPad, or iPod touch - Apple Support

Go to Settings/Screen Time/Content & Privacy Restrictions/iTunes & App Store Purchases - Change Deleting Apps to Allow.

i tried doing that, but it still didn’t work.