In guitar pro 6 I need to learn how to remove a specific string without damaging or altering the sheet music that the string is on. In a certain score of music, a guitar part does not have any notes on that string and will make it easier for the reader to learn and read without that string. If you go into properties of the profile for that instrument it lets you change the number of strings, but just takes the top string off without giving you a choic.
You can't remove a specific string.
As you noticed, you can choose the number of strings but it will remove the top string and you can't choose to remove a string in the middle of the others.
Yet, what you can do is to create a new track, select the number of string you want and change the tuning of each string to match the ones you want to keep and copy/paste the notes from the full-string tab to this new tab.
You might have to fix some positions but GP should manage to keep all the notes if it can.
I'm not sure GP allows you to put any tuning on any string, but it is worth a try.
But I don't think this is a good idea. I don't think it will make the tab easier to read, and I don't think this is a good way to learn to read a tab. It is important to be able to identify the string on a glance, and you do that by checking to position relative to the others. Removing those will hurt your ability to read more than help.
Moreover I don't think this is a good idea to learn something that is not "the real thing" as it will make learning to read "real" tabs harder.