Join eRWin for 24 hours @ $36 and you can download the service manuals there; You cannot buy a paper manual for 2012 to 2019 VW beetle. The only source for repair information is from Volkswagen you can try eRWin site, which is VW's online repair info site, to download the manuals or there are other services that provide access but you cannot download the manual; all data and Mitchell one of those. The third-party services are just licensed from VW service info.
Check your pm. The only fuse I can find is the ones for the alarm horn. I even looked at the wiring diagram for that system and I can't find a fuse just for the horn. But I agree with Billymade about getting the manual from volkswagen. If it's the price. You get what you pay for. It's downloadable. Tons of information. If you are going to dyi your car. I recommend it. Mine only works with the key on too. And if I don't use the middle of the horn "button" it won't work. It's like everything else, picky 😂. To my understanding. The fuse 'card' was in the original owners manual from the factory. But if you got your car used like me. Then your's might be gone like mine was.🙄
If you can access the horn; you might jumper 12V to it and see if it works. If it does, you then, need to work backwards, to find out why.
A vw scan tool, would help you; scan for trouble codes and do output testing, to activate the horn without pushing the button. VCDS by ross tech and OBDEleven, are the most popular VW specific, factory level scan tools.