How do you complete a tree shortcut to level up or finish a skill? I did note that you do not receive Lingots if you do that but I'm okay with that. Assistance please.
If you scroll to the bottom of the screen, you'll see a few grey words: "About / Duolingo / English Test" and so on.
Hit "help", then scroll a bit down to the section "Using Duolingo". Hit "see all 21 articles". Look for "How can I skip the basics".
The help center is Duolingo's version of "just google it", and it's generally considered good form to look up things there first. Probably because Duolingo is by now so well-known that there are always a lot of new users, and they can easily swamp the forums with basic questions.