Hi all!
I'm a fan of making my Werewolves and Vampires star-crossed lovers, so I'm trying - with genuine difficulty - to start on a mod that will make them like... Not necessarily hate each other less, but there are amazing benefits for both in a partnership when they've overcome their differences with that "sympathy from werewolves" thing. We're going for Romeo and Juliet vibes here. I have no illusions about my modding skill (it's so green ) so I turn to you friendly folks for advice. I am starting small, just changing the Dog Water buff to something that makes the Vampire Happy instead of Angry.
I already have Studio, and Notepad, with the XML files extracted, and so far this is what I have edited in the new file for the buff:

So, few questions:
1: How do I get to the InGame folder? I want to swap the icon of the buff but I can't seem to find what folder it's in. I don't really want to upload a new one, just copy a generic werewolf or like, alcohol icon over from the game's files. If it's easier to just find a Happy Moodlet that has the icon I want to copy the I'm totally down for that and any recommendations
2: Do I need to mess with the DATA folders? This did not imply I did, but I'm messing with UI, so if I do and S4S won't do it for me, how to access those would be phenomenal!
3: Any advice on later add-ons (Vampires and werewolves with the 'Soulmate' relationship state can hunt together/werewolves getting some kind of fury reducer similar to somber howl from being comforted by their vampire mate/etc) I know those are beyond my paygrade now but the idea is delightful
4: Playtesting advice. I plan on releasing it publicly when the barebones are finished but I've never playtested in my life! Help, lol

Thanks all! Much appreciated if you gave this thread a look-see

1. You don't, and unnecessary to edit for modders. All that matters is the numbers next to the name. You can either extract a list of icons with S4S using the cheat list.icons (open cheat box same way as in the game) to copy the group (middle numbers) and instance (last long number) over, or open an existing EA file and copy over, or open Tools > Game File Cruiser and manually search (do not recommend) to copy the numbers over.
2. SimData must always be updated when you update the same sections in the tuning file of the Buff, or any file that comes paired with one. When you extract tuning with Studio it will extract the SimData it comes with. I would recommend looking at this tutorial instead: https://www.patreon.com/posts/tutorial-lets-31903086
3. For the last idea, I would recommend looking for the Somber Howl interaction to study how it works and what files it references. But mainly you'd make a custom comfort interaction (easiest option to avoid conflicts) and then add the same loot from the howl to the outcome of the comfort interaction (tutorial on making custom files here). For the first idea, not sure what to suggest for that as I can't remember if the pack came with group hunting, but basically look for a similar interaction in-game to clone, that way you only need to change a few things like the tests and outcomes.
4. Test your mod alone with no overrides/game changers installed (other than requirements like XML Injector), this way you know it for sure works by itself. Then you can dump all your regular mods back in for a final play through to see how they interact.