When resizing the launcher window horizontally some UI controls are not displayed anymore when the size becomes smaller than a certain threshold. In the attached images you can see the window with a different horizontal size (just one pixel) where in one image some controls are not displayed while in the other they are.

Affected controls are (as far as I know) the "Download server" link as well as the "Browse..." and "Go to folder" buttons when editing a launcher profile.

As can be seen in the images this threshold is not very low, i.e. one encounters this issue already with a normal window size and not only for ridiculously small sizes.

To reproduce go to the "Launch options", click on a profile and vary the horizontal window size. You will observe the text box of the game directory to snap closer to the window edge, replacing the buttons next to it.