Does anyone know how to slow a unit down by putting a burrowed unit under it and removing it? I've tried creating a burrowed unit under the unit I want to slow down, and then removing it in the same trigger, but it does nothing. If anyone could tell me, that would be great, thanks.

Burrowed units are displaced when you create them directly under another unit. What you need to do is creating them somewhere else and moving them under the unit you want to slow down after.

Alternatively, you can slow down your unit by creating air units above it.

Alright thanks, I found a good solution