For the searcher, here are the top three sources:
That night, she didn’t analyze with Stockfish. She opened Polgar’s PGNs again and filtered for “rook lifts” in the middlegame. Thirty-seven examples appeared. She played through each one, covering the annotations, guessing the next move. Her accuracy rose from 64% to 81% in those positions within a week. laszlo polgar chess middlegames pgn better
Use Polgar’s 5334 Problems (Ch. 5–7 are middlegame combinations) or Chess Middlegames (out of print but available as PDF/DJVU). Each problem is a position with a clear goal (win material, checkmate, or gain advantage). For the searcher, here are the top three
Load a single PGN position onto a physical board (or a blindfold mode online). Do not move the pieces. For the searcher