Great feedback.
I'll see if I can make the Leave-button a bit more prominent. Just saying "Leave playtest" would make it a lot more intuitive.
I see the issue. In earlier versions of the game I had a full automation builder where you could configure any rule. Since then, I've tried to strike a balance between UX and flexibility. The idea of custom ranks is interesting, I'll explore it a bit.
It's pretty hidden at the moment. If you hover cards in your deck when the deck is docked in the right nav, there will be an outlined heart-icon that set the deck image.