RUDE ENGLISH, HOPE YOU WILL UNDERSTAND EVERYTHING I WROTE.

Good news, everyone!

This guide will let you make your own standalone item mod, not just retexture.

1. Tools.
Nifscope
B.A.E.
FO4Edit
Gibbed's tools
Do not forget to endorse tools authors, cause standalone modding ability is 99% their merit.

2. Unpacking.
Use Bethesda Archive Extractor to extract game archives (ba2 files). I recommend to extract all of them once, and then work with extracted files.
Simply run BAE, hit File -> Open file... Choose ba2 archive, then choose the folder, where you want to store unpacked data (i.e. C:\FO4\data\) and hit Extract button.


3. Editing.
At first, you have to locate all the files you will need. I'll pick the red flighting helmet for example.
Every ingame item have Model file (.nif), some materials and material effects (.bgsm and .bgem), and some textures (.dds).
Open FO4Edit, and choose the fallout4.esm file. Then you need to find the base item you want to edit and add as standalone.
Here is fo4 item id's, that can help you finding object id. Input ID into the FormID field adn hit enter. Here is what you will see (well, not exactly):


Here we need to locate the model file. It's Armor\FlightHelmet\Helmet01GO.nif. So the first model is located in C:\FO4\Data\Meshes\Armor\FlightHelmet\.
Then look at this "Armatures" list in the bottom. There is two references - AA_FlightHelmetRed and AAHelmetFlightCap. Letters in square bracers shows where to find them, ARMA means armor addons, hex digits is FormID. Let's look at them


There we found some more models we need (in my case there was only helmet01.nif needed, at least for now).
So, for this moment you have some models of your item. Let's take a look.

3.1 Editing model.
Open NifScope and load first extracted model (Helmet01GO.nif in my case). You have to set correct paths if you want to see it textured.

At the block list (left column) you can see some links on the materials. For me it's Materials\Armor\newFlightHelmet\Helmet01.bgsm and Materials\Armor\newFlightHelmet\Glass01.bgem. So, we will need to modify them later. Now we need to change paths to the textures and materials. I just added "new" to texture folder names (so there is FO4\Data\Textures\Armor\NewFlightHelmet\some_dds_files.dds). The same with materials.
IT IS VERY IMPORTANT to set all this things correctly, like it was in original (no absolute paths, the default is FO4 Data folder, to start from, so textures paths starts with textures\, materials starts with materials\, etc.). When you changed everything you need just save the model with a new name (or just in new folder). Then repeat all this for other models (in my case it was Helmet01GO.nif and Helmet01.nif).

3.2 Editing materials.
Use Gibbed's tools to convert .bgsm and .bgem files to .json format. In my case there was only two files needed - Helmet01.bgsm and Glass01.bgem.
After covertin them to .json you can delete .bgsm and .bgem ones, and just change json files extentions back to bgem and bgsm. The game will understand them correct. Use Notepad (i'll recommend Notepad++) to edit those json files.

Here we need to edit paths to the texture (again, right).

3.3 Editing textures.
There was some tutorials on texture replacing already, so I will not rewrite it again.

3.4 Making an ESP module.
Now we need FO4Edit again. We need to copy needed forms to a new file. Needed is Armor\Armor_FlightHelmetRed and Armor Addon\AA_FlightHelmetRed. Also, there should be the way to find this new item in the game, so I copied some other forms as well.

Here I've added my new helmet to some lists like raider helmets, random helmets, and settlement vendor sell list. To add item in the list right-click on the right field (chosen on the screenshot) and click add. Enter Level and count (Ive enetered "1") and input the reference - the main modded item FormID (1000800 in my case). Save your new ESP.

4. Everything else.
Add your created files into your falluot 4 Data directory, so there will be an ESP file and Materials, Meshes and Textures folders. Enable your mod in mod manager. Start the game and check that you did everything correct. In the console (~ key) print command "player.additem ItemID" without commas. In my case it will be "player.additem 1000800". If you use other mods you need to restart FO4Edit and choose all the mods you use. You will see that your ItemID is changed because of mods load order.



I hope I didn't forget anything. I'll put my helmet mod here just as example, or if you want to endorse this tutorial.