Author here, if you want to ask anything ...
Thats all for now, thanks.
1. Code block is exited by double enter (so two new lines)
2. No shortcut for the checkbox unfortunately
3. Only Themes can change the fonts - see e.g. "Steel Blue" in the demo document to see how it's done. https://github.com/zadam/trilium/wiki/Themes
4. You could use custom CSS to change it however I can't recommend this: https://github.com/zadam/trilium/wiki/Themes#custom-css