Every modder needs proper tools, just like every lumberjack needs a swingset. This list does not claim to be a sure-fire solution to every single issue a modder might face, nor an impervious list of perfect programs, designed to cater your every need. This list does have a lot of value in it, I believe, and if used correctly, a lot can be achieved.
You'll also notice that this section has random housed tutorials in it, that don't fit in any particular place with the larger-scale tutorials. The author and summary of each will be listed and maintained here!
Kaedrin's Mod Manager is a very useful alternative mod manager that works for all Total War games since Total War: Empire.
You can get in contact with the creator, Kaedrin, in the Modding Den's channel #kaedrin_mod_manager.
RPFM is a great pack-file managing tool, essential for any modder. Active development has new features coming regularly, as well as constant bugfixes or squashings.
Get in contact with the creator, Frodo, in the Modding Den's channel #rpfm.
Mod Troubleshooting Guide by Cataph - An overview of how to debug any mod issues, as a user.
Tolerant Tables by Cataph - A list of different tolerant tables, a really helpful resource for peeps who want to do some intricate sub-modding.
Unit Card Guide by Cataph - A helpful series of guidelines on how to create a new unit card. Includes a template file to start off with.
Building Buildings by Vandy - A tutorial for creating custom buildings from scratch.
Creating Custom Units by Cryswar - This guide is meant to walk prospective modders through creating a new unit in TWW2 using RPFM, assuming little to no knowledge of modding.
Creating a Custom Legendary Lord by Cryswar - This walkthrough will walk you through creating a bare-bones custom lord and adding them to the game. It assumes you know the basics of modding and how to create a new unit, covered in the previous guide.
Custom Skills, Items, and Effects - Here we discuss how to edit or create custom character skills, ancillaries, and effects, then attach them to each other as desired.
Creating and Editing Abilities - We will cover how abilities of all types work - unit abilities, augments, army abilities, vortexes, etc.
Setting Up GitHub Desktop for Total War - A rundown on how to setup GitHub Desktop for use with the Assembly Kit.