I am looking for a program for Windows or an online service for viewing PGN at variable speed. I know that lichess has fast and slow speed, but I want more adjustable settings.
My own web application can help you
(1) Paste the PGN text into the 'PGN import' tab.
(2) Adjust the speed of animation on the 'diagram' tab.
(3) Click 'download animated diagram'.