So, in general the ui is very 'discoverable' - you can very much figure out what all the icons mean and the buttons do, and the tooltips are useful. But there's a few exceptions:
the timeline panel...I had no idea that even existed until I saw that in somebody's video, and it's a pretty crucial part of the program
holding the left trigger (oculus) to get the frame options - I did that a couple of times by accident and then just could not find it again
sliding the layer name in the layers panel reveals lots of new options, but I only found that by accident
I have a sneaking suspicion there's other similar stuff that I haven't found - I mean, who knows, right :-)
So, in general the ui is very 'discoverable' - you can very much figure out what all the icons mean and the buttons do, and the tooltips are useful. But there's a few exceptions: