This is just a test to try and figure out how the rename hyperlinks instead of just calling for example " https://www.gog.com/redeem/"

Well time for some tests until I get an answer. :)
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AB2012 explained it better and simpler than I did, so I'll delete my messy attempt as describing the solution I came to during my testing lol.
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The url needs an opening and closing quotation mark ( " ) as well, doesn't it?
[ u r l = "h t t p s : / / w w w . g o g . c o m / r e d e e m" ] Description[ / u r l ]

It might on some forums / proper HTML but I don't think GOG needs it. At least replying to people's posts that contain URL's, GOG doesn't seem to insert them in the quoted part and they still seem to work.

No. I've never used quotation marks in any of the ones I've done.

Thanks for all the replies everyone. I figured it out as soon as I posted and was in the edit screen to update, so I didn't see all the replies yet.

I'll mark the first reply as the solution since I don't think I can mark multiple ones.

Thanks again all. Community is always helpful here. =)
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Note that you may need to replace some characters. Most commonly ( and ) with %28 and %29. Also "url" must be lowercase.

Let me do some testing of my own:

Just the link:
https://en.wikipedia.org/wiki/The_Witcher_(TV_series)

With % stuff:
https://en.wikipedia.org/wiki/The_Witcher_%28TV_series%29

URL uppercase:
[URL]https://en.wikipedia.org/wiki/The_Witcher_(TV_series)[/URL]

Just the link with lowercase url tags:
[url]https://en.wikipedia.org/wiki/The_Witcher_(TV_series)[/url]

Named link with lowercase url tags:
The Witcher TV series

Named link with lowercase url tags and %stuff:
The Witcher TV series