Puzzle Studying

I’ve been kind of wanting some kind of training mode with the puzzles that can quickly hone in on ones that are close to my skill level. I have thoughts on how that would look, but thought I’d search around for prior conversations along those lines. I’m a developer so I’m mostly looking for ideas/feedback before I start on such a project.

I was intending to start modestly, just having a way to resume a puzzle collection where I last left off would be nice. I was surprised to find a thread from 2014 discussing something very similar, but for the life of me I can’t find anything related to that in the interface.