This code means that the variables used by this skin are all in the Variables.inc file in the settings folder under the skin file.
In other words, if you need to modify anything provided by the author, you should look for it in this folder.
Unfortunately, there is no player code in the code you provided, which means I have no way to know that this skin is made of aesthetic player plug-ins.
You can go to the Variables.inc folder to see if the author has any notes.
╮ (╯ _ ╰) ╭ Different player plug-ins are associated in different ways. Visual inspection is a quantity player made of nowplaying plug-in, but the specific variable name is unknown.