First of all, if you want to be able to change the name, you have to be sure that 1.16.5 is it's own installation, not under "Latest Release". To create an installation, go to the "Installations" tab the click on "New". There, you can select your version (1.16.5), an icon and the installation's name. There is also some stuff that you probably don't want to touch. To change the name of an installation, click on the three dots to the side of it then select "Edit". Hope this helps!