This is the big one, Retoc with Tuw GUI, it'll handle unpacking and repacking our mod files as it also manages to keep them in formats that you can edit with UAssetGUI and then are repacked for the game to be readable.

The tool of choice for modding uassets, usually data files, I'm afraid this guide will be biased towards datatable editing as I have no experience with textures-models-sfx editing, but I assume the extracted files will now be in a format where tools that worked in UE4 games will maybe work here now as well.

Only needed for extracting Mappings.usmap file which is needed for UAssetGUI and FModel if you plan on using it. You'll want to extract it into the games Binaries/Win64 folder then editing the ue4ss-settings ini file to enable the console, so that you can easily at startup just navigate in the console GUI to the dumper tab from where you can dump the file which is generated inside the Binaries/Win64/ue4ss folder.

( https://github.com/4sval/FModel/releases )
FModel which was a staple and useful for individually extracting files before, sadly is unable to do so now in formats we can easily modify, but it is still useful for exploring and streamlining retoc unpacking if you don't want to unpack entire games worth of data that you won't even touch (45gigs in this case)

So, you've downloaded the tools.
You've maybe slapped the UE4SS files quickly into the games folder (\Steam\steamapps\common\AlienRogueIncursionEE\Midnight\Binaries\Win64) the dwmapi dll and the ue4ss folder next to the Midnight-Win64-Shipping executable, then edited the UE4SS-Settings ini file inside the ue4ss folder to enable the console
[Debug]
ConsoleEnabled = 1
GuiConsoleEnabled = 1
GuiConsoleVisible = 1

Start the game, dump the Mappings file, quit, you can delete/move the dwmapi dll because you won't be needing UE4SS anymore and it's a resource hog.

Then you can set the local mappings file in FModel as well as UAssetGUI if you want.

Remember, FModel is ONLY FOR REFERENCE! We will NOT be extracting with FModel assets as they will be in a useless format, retoc does all the heavy lifting, but FModel is useful to have open in the background to refer to folder structures because you can filter in retoc what you specifically want to extract with for instance
As an example, so it only extracts those folders and their subdirectories if you don't plan to mess with anything else.

Retoc Tuw GUI is so simple this guide will be rather brief.
In the top-left Menu you'll select if you'll be unpacking or repacking, and you'll be using Retoc for both, NO OTHER PROGRAM.
Don't tick any boxes (mine all were unticked by default and I left them like that), just fill out the Input & Output parts and making sure engine version is correct (5.5 in this case) and adding optional folder path filters if you don't want to extract everything.

Now, with these extracted into some Output folder of your choosing, they're in classic uasset/uexp combo formats that you can open up with UAssetGUI, of course UAssetGUI needs the Mappings.usmap file and correct (5.5) engine version which bears repeating, but then you can edit as you could in the past 99% of UE4 games.

Retoc change in the top-felt menu to repack your changes, you can make your own folders, inputs and outputs which is the name of the mod, remember that UE4/5 mods it's wise to name them something like z_INSERTNAME_P.utoc, the "_P" is a "patch" signifier for the engine from what I've read, also just remember to keep inside the correct folder-paths as usual (Midnight/Content/etc).
And it should work!

Retoc for unpacking-packing and it handles all file format changes, tool of your choosing to edit files (UAssetGUI in this case), Mappings files usually needed and extractable with UE4SS
- I did already upload a Mappings file for ARIED for the current 1.0.3 version of the game if you have trouble with UE4SS
https://www.nexusmods.com/alienrogueincursionevolvededition/mods/2

I got so excited when I could actually open & edit the files that I tweaked a ton, put them in game, tested only a few minutes and rushed to put out this guide.
I'll be uploading some mods soon, planning on uploading a pack where you can choose what you want out of Xeno AI tweaks, Player Health buffs as I've mentioned in previous posts to compensate for Xeno aggression increase, and an optional file buffing Pulse Rifle damage from 35 to 45, didn't feel like going mental with it at least this early in testing (I did also slightly make Xenos a tad weaker but not by a ton, 10% more damage on Expert and 20% more damage on Normal), they're all in separate modular pak files so you can choose, at least somewhat what you want (Xeno pak file contains a lot more, some lurk encounter changes, multiple files that go over taunt chances, stuff controlling the min-max timers for lurks and investigations etc, added more "randomness to it but it can also mean longer quieter moments, will have to see in testing).

Got done uploading my modding efforts, in case people want an excuse to test out some differences to Xeno AI on different difficulty settings (includes a lot, see readme/doc)
https://www.nexusmods.com/alienrogueincursionevolvededition/mods/3
ModdB mirror:
https://www.moddb.com/mods/alien-rogue-incursion-balance-overhaul-collection/downloads/aribalanceoverhaultweaks

Anyway, that's it for now. Nathan signing off.