Would be so good to have this back, for all platforms to be honest. When you do beta or internal testing and push a lot of builds, it's extremely useful to verify people are on the right build. Having them open the manifest file to track that down is infinitely more painful. Thank you!
Agreed. Please kindly add content build id as before.
I have it in beta in updates tab
I guess ticket can be closed

It appears it's still impossible to copy the app or build IDs easily, making it easier to make mistakes when sharing. I'm leaving the issue open requesting that this is solved, for example by making it possible to select the text (to then copy with a shortcut) or by making the IDs clickable which would copy them.
Admittedly I liked the App ID being immediately visible when opening the dialog by being on the sidebar, but I guess it does make sense to group them all together. Hiding the build time when it's not available is a nice touch too.
Regardless of the resolution, thank you for hearing us out and bringing the build ID back.
proton 5.13x1 2020-12
Your system information
Please describe your issue in as much detail as possible:
A recent update of the Steam client added the app id to the app properties window, but at the same time replaced the "content BuildID" string with a "content release date" instead. Unfortunately, this date is less useful than the previously displayed BuildID, especially since for some apps the release date is not filled out (Proton 5.13 and SteamVR both display "Jan 1st, 1970").
I would like to request that the BuildID is brought back to the app properties dialog, as it makes diagnosing issues easier.
Additionally, it would be convenient if one could copy the BuildID by clicking on it.
Steps for reproducing this issue: