Hello,
(minor issue) I noticed that in the new Liquify layer the first use of Undo removes the last two strokes of brush, (and then each subsequent Undo removes only the last brush stroke - as it should be). However, the Redo puts back only one of the two removed strokes (the very first stroke, if undone, cannot be restored with redo).
How to reproduce: open any image, add Liquify layer, select any brush, deform the image with 2 strokes, hit Undo (both strokes are gone), then hit Redo (only the second stroke reappears).
Affinity Photo Mac 1.9.1 on MBP 13
Best regards,
Tom