Still broken in 1.20-pre1.
Please consider fixing this for 1.20, it affects my enjoyment of the game.
Checking those seems to have fixed the issue, thank you.
A little UI feedback: this is confusing design. Those boxes read as filters to what is displayed. As you can see, with no boxes checked, everything is displayed, which reinforces that those would limit what is shown and that it's not necessary to select them if you want everything. It makes no sense at all that unrelated functions on other screens (Create new installation, Edit existing installation) completely fail if those boxes are not checked.
Suggestions: Either align the two behaviors (no boxes checked = display all installations and make all versions available in the drop-down, or no boxes checked = display no installations and make no versions available, but not half and half) or put some red error text on the screen when nothing is checked instead of blank UI that acts like a broken application.
Here is what the 'installations' tab looks like.
The launcher knows about versions like 'fabric-loader-0.12.12-1.17.1' but it will not show them in the drop-down, nor allow them to be edited. It can successfully launch any of these, I just can't add any without using the Fabric installer or editing the .json file by hand.
Still broken in 1.20 release.