Hi! Whimtale is exactly as you said it: a simple engine for hobbyists. If you want to make the next Hollow Knight, you have to look at other engines. Whimtale takes the concept of Bitsy games and improves on it and the Bitsy editor structure, allowing making more dynamic stories, but the scope is still limited. You can look at the bitsy tag at itch.io to see examples of this game style.
If you’re unsure, check out the online or desktop versions first, as HD and Ultra editions are based on the same core and only add stuff on top of it — meaning that programming and exporting capabilities are the same.
About Windows export, Whimtale produces only html files right now — which can be opened in any browser, but definitely is not a native steam-like experience.
Feel free to ask any other questions!