Instructions for basic TASing can be found on KlimbRio's amazing project. What changed is that instead of "TAS 1-9" it is now "TAS YOUR LEVEL". which can be edited in the level editor. When you press q+m, it takes you back to the start and tests your TAS. Pressing q+c will automatically turn on hand-playing mode and not reset your position.
Thanks to @caldrika and @KlimbRio1 for their amazing TAS maker, and of course to @griffpatch for making Appel.