A Programmer's Guide to Karaoke Templaters
I wrote a guide explaining how Aegisub's karaoke templaters work by going through a simple example. The page also describes the major differences between the three big existing templaters and how to migrate from one to the other.
Link: https://github.com/TypesettingTools/arch1t3cht-Aegisub-Scripts/blob/main/doc/templaters.md
In hindsight, the name "A Programmer's Guide to Karaoke Templaters" may have been too intimidating. The thought process behind it (apart from wanting a catchy name) was that the guide only explains what a templater does, and not how ASS tags or Lua scripts work, so that the perfect target audience is somebody who is already experienced with typesetting and programming, but not with Karaoke templaters. But this made some users think "I'm not a programmer, so this guide isn't for me." Oh, well.