Some games have way too long names and they literally leave the space of the left panel. In order to read the whole name one sometimes has to drag the panel border to the middle of the screen which I find ridiculous. So I suggest an option to be added in the Steam client for all platforms (Widows, Linux) to change the name we can see. That won't change the app ID or the actual name in the right panel when you click on the new name, only the name we see when we run the client.
It could be in right click menu --> Manage --> "Rename". And, if one wants to go back to the original name, the "Rename" option will become "Undo renaming".