Hi Jeffrey, thanks for getting in touch!
Glad to hear that you're syncing with Trunk Notes, it's a great app. I have to admit that I always use square brackets for my WikiWords, but that's possibly because I have a lot of code snippets in my wiki that I don't want parsed as links. Would certainly consider adding it as an option though for better consistency with Trunk Notes.
Custom CSS is definitely on the cards, maybe with some selectable themes at first - anyone else want a dark theme for the editor? - followed by the ability to add raw CSS.
I'm struggling to get the app updated to the latest version of the application framework that it's built in at the moment, but once that's done we can get back into feature development.
Cheers,
mark