can anyone explain to me how the fancy bets tab work?
I have already deposited but no clue how to use it.
Regular betting works very smooth, though!

It's just a visualisation of your betting. Output only. You use the panel above to bet (or the weirdly undocumented keyboard shortcuts) just like with regular betting.
Oh man, yeah, we do need to document those, I'll do that right now, and I should probably add a blurb about how fancy bets works somewhere too. Man I'm never gonna get a chance to finish ma' soaps!