I had a bug report about a similar UI problem, it may be connected to it. (MC-151412)

The bug

When you are in the multiplayer menu if you go to the edit / add server and menu you can select the Server Adress section just fine, but if you select the Server Name panel, again, both panels show the selection like a multicursor tool would do that.

Strange enought that editing works just fine, and you can only edit the section you meant to edit.

It not appears if you use tab + shift tab for recreation.