This looks like a really cool tool for visualizing proofs in Lean:

https://github.com/Paper-Proof/paperproof

https://lakesare.brick.do/lean-coq-isabel-and-their-proof-trees-yjnd2O2RgxwV

This will probably get unweildy very fast for even moderately-sized proofs. But I suspect that it’ll be of great help for beginners.