As just a mod user: once you download BG3 Mod Manager and Script Extender and BG3 Mod Fixer, you're good to just start adding stuff, and all you have to worry about is when the mod was last updated, and load order for mods that change the same things... And of course, Script Extender being the work of one person and it has so far needed a few days to get patched after every other patch (so there have been weekends of people not being able to play, which does admittedly get solved by not having the game auto-update).
As a modder: Because of the engine being the same as used in the Divinity games (and years of early access), the modding community had tools ready to go from the start, which actually makes modding it possible. So given the use of LSLib and BG3 Modders Multitool, you can (eventually) find what you want to change (as long as you are ready to do some detective work, and follow IDs back to other entries that list other IDs for you to follow, so one of them will do what you want). And for visual things (meshes and textures), Padme4000's Youtube videos will guide you along. So you know, you can easily make changes with those tools, it's just cumbersome. And occasionally Larian may
still change their file formats (like moving all of the individual textures to be read from a big combined virtual texture file instead, which made sense to make the game work on XboxS, but caused a lot of extra work for modders).
Difficulties as a starting modder: The structure is a mess (there are files that are named the exact same, because the folder structure is split into early access / full release sections, and sometimes they cover completely different entries but sometimes they cover the same ones and rely on the latters overriding the first ones, and for example, the base rigs of the player race heads are thrown in 3 separate folders on top of that). Sometimes the files are packed (all called _merged.lsf), sometimes they're not (like CharacterCreationAppearanceVisuals.lsx). Inheriting parent entries sometimes works (Grease spell's effect PRONE_GREASE is using PRONE effect as base, only listing what is different), but often not (changing partymember appearance is not just one entry, but there's multiple entries for different cutscene needs, but at least their skin/hair/eye colors use one shared file), etc etc.
Personally, I have steered clear of Script Extender reliance until the game is in a more stable state (and I've purposefully limited myself to mods that won't invalidate my save files in case I had to remove all of them). You can do a ton of stuff with just directly putting changed files into the Data folder (called overriding), so let me see what I've put in (some of this is actually my own work, but all of those rest on first looking at someone else's mod to see how something similar was done)...
- skip Larian logo and pressing any key at main menu
- clean UI (removed minimap, hid buttons, hotbar and such get hidden if you're not mousing over them, movable combat log)
- removed loading screen hints (because there's only like a literal dozen of them) and added official art book pictures to the loading screen gallery
- tried to improve the AI over some dumb things (like its love of triggering opportunity attacks, though there's definite limits here, some things the AI is just going to be stupid about, it's very possible the person who created this AI system for Divinity is not even with them anymore)
- fixed stuff Larian has just left broken (like Totem Barbarian Rages, or some half-feat stat gains not stacking with other things that boost your stats, or Halforc Durge losing their racial skill instead of getting to pick a skill when the background already gives that skill, or base game outfits having your Halforc butt/thigh clip through them, Prone breaks concentration, etc)
- changed Dragonborn scale color options, replaced halforc heads with prettier ones (had to fix neck seams in Blender), reduced the effect of the default wrinkle maps and halved the green level of halforc head textures to make them match body textures better (had to install something that reads DDS files), changed piercing sets
- added custom hairstyles, and copied all the hairs to show up in beard/horn/tail categories as well, so you can mix-and-match styles
- changed Wyll and Gale into women, which sadly did not make Wyll any more interesting, but it made me give Gale a proper chance and she's proven amazing (and Gale's voice acting really works through the AI changers, which tend to flatten a lot of the others)
- relatedly, in Patch 6, Larian changed the audio format of dialog lines to use a much worse, lossy, crappy compression format, but at least a modder converted 25gigs of the original voice lines into a better-quality version using the new format
- changed Shadowheart into Gnomeheart, just to have someone represent the shorties... but while everything worked, as NPCs end up walking more than your controlled character who just runs everywhere, the gnome walking animations just looked too silly, so I reverted this change. I still want to make someone a dwarf, but there's a lack of dwarf-y voice changers, and playing around with audio files using the proprietary Wwise is not my idea of fun
- made the Tactician+ enemy roll buffs scale with player level (and apply to enemy saves as well)
- a lot of small things (raised long rest supply cost to 200, changed character creation's black hair color to actually be black instead of gray, removed Honour mode's single-save limit, changed initiative die to use d20 instead of d4, raised XP requirements by +30%, changed the background/camera position of portrait poses, better environmental textures, less absurdly large staves, etc)
I list all this just to give you an idea of what you
can do, without relying on the Script Extender. With it, things will eventually get really crazy, as you can randomize a buff to give each enemy when combat starts, you can walk around with all of your party to see their interactions but only a random three join you in any combat, there'll be an animation framework pretty soon (!!!)... it's core enough to many people's modding experience/expectations, that I really wish Larian just packaged it in (but I guess the access to Osiris/Lua scripting in theory opens up some malicious options, so I'm not expecting that to happen).
"Small" is relative compared to the giant pile BG3 made. Then too, I doubt a full-blown sequel would have made less than BG3. I think Larian's decision was more about artistic freedom than economics though. Assuming they had the opportunity of course. They do have a reputation for producing good games (and I've played several), I just hope they don't regret passing over a sure thing.
