I am not an English speaker. Most of them rely on machine translation. So it's hard to explain more.
If you are familiar with these topics, please help people who are in trouble.

I've edited some sii files for vanilla accessories. So you may experience conflicts with other author's mods. So I'll give you some examples to show you how to avoid conflicts.
I'll also give you an example for those who want to combine my mod with other author's mods.

Caution
Do not edit directly mod files. if you do that, those files will be overwritten automatically by steam workshop when the mod author update them.


First, please download this file[pete379jp.s69.xrea.com]. I created a template for the patch mod.

Then unpack downloaded file into the directory below.
C:/Users/USERNAME/Documents/American Truck Simulator/mod

Like this.
C:/Users/USERNAME/Documents/American Truck Simulator/mod/Peterbilt_389_Patch

You can change the folder name "Peterbilt_389_Patch" if you want.
Delete the downloaded zip file because it is no longer necessary.


(vanilla accessories)
For example, Day Cab interior "Premium Ultra Ride" conflicts with the other author's cabin.

1. Copy "duty_lux.sii" from my mod.
Your steam install path .../steamapps/workshop/content/270880/1236296810/latest/def/vehicle/truck/peterbilt.389/interior

2. Paste it to the directory below
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/interior
If there is no folder, create it from the context menu of the right mouse click.

3. Open both my "duty_lux.sii" and the other author's "duty_lux.sii" on a text editor.
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/interior/duty_lux.sii
.../steamapps/workshop/content/270880/xxxxxxxxx/xxxxx/def/vehicle/truck/peterbilt.389/interior/duty_lux.sii

I recommend to use third party text editor like Notepad++.
The sii files uses a different code than the Windows line-breaking code. So Windows Notepad doesn't display them correctly.

4. Check the unit "suitable_for[]:".
Compare my "duty_lux.sii" with the other author's "duty_lux.sii". There should be a difference in the suitable_for[]: section.
http://pete379jp.s69.xrea.com/image/steam/Peterbilt_389_Pack_patch_01_01.png

5. Copy and paste
Copy the unit(s) from the other author's "duty_lux.sii". Then paste the unit(s) you copied to my "duty_lux.sii".
http://pete379jp.s69.xrea.com/image/steam/Peterbilt_389_Pack_patch_01_02.png

Save (overwrite) "duty_lux.sii". It's done.


For example, use the other author's interior mod in conjunction with my custom cabin.

1. Copy "awesome_int_duty.sii" from the other author's interior mod.
.../steamapps/workshop/content/270880/xxxxxxxxx/xxxxx/def/vehicle/truck/peterbilt.389/interior/awesome_int_duty.sii

2. Paste it to the document folder.
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/interior/awesome_int_duty.sii

3. Open both sii files of my custom cabins and "awesome_int_duty.sii" (you pasted) on a text editor.
.../steamapps/workshop/content/270880/1236296810/latest/def/vehicle/truck/peterbilt.389/cabin/m1_duty.sii
.../steamapps/workshop/content/270880/1236296810/latest/def/vehicle/truck/peterbilt.389/cabin/m2_duty.sii
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/interior/awesome_int_duty.sii

4. Check the unit "accessory_cabin_data:" in my cabin files.
accessory_cabin_data : modified1.duty.peterbilt.389.cabin
accessory_cabin_data : modified2.duty.peterbilt.389.cabin

5. Copy and paste
Then copy these strings above to the clipboard. And paste them under suitable_for[]: section in "awesome_int_duty.sii".

6. Modify strings
Modify pasted strings like this.
suitable_for[]: "modified1.duty.peterbilt.389.cabin"
suitable_for[]: "modified2.duty.peterbilt.389.cabin"
http://pete379jp.s69.xrea.com/image/steam/Peterbilt_389_Pack_patch_02_01.png

Save (overwrite) "awesome_int_duty.sii". It's done.


1. Move the files manually.
Copy (or cut) the files you want, then paste them in one directory above.

Copy (or cut) from:
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/paint_job/DLC files

Paste to:
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/paint_job

It's done. You don't need to edit these files.


1. Copy "super_cool_ab.sii" from the other author's paint job mod.
.../steamapps/workshop/content/270880/xxxxxxxxx/xxxxx/def/vehicle/truck/peterbilt.389/paint_job/super_cool_ab.sii

2. Paste it to the document folder.
.../Documents/American Truck Simulator/mod/Peterbilt_389_Patch/def/vehicle/truck/peterbilt.389/paint_job/super_cool_ab.sii

3. Open the file and add the unit.
It is a little different from the method shown above. it use the "sui" file(s).
I have already created sui files in the paint_job folder.

suitable_for_mod_cabin_a.sui This file is for my Duty cabin (Day Cab).
suitable_for_mod_cabin_b.sui This file is for my Standard cabin (Low Roof Sleeper).
suitable_for_mod_cabin_c.sui This file is for my Exclusive cabin (Ultra Cab Sleeper).

In this case, "super_cool_ab.sii" is a file for the Day Cab and Low Roof Sleeper.
So add "suitable_for_mod_cabin_a.sui" and "suitable_for_mod_cabin_b.sui" to "super_cool_ab.sii".

Like this. These strings must appear at the beginning of a new line with no whitespace (space, tab, etc) before it. Visit SCS Software Modding Wiki[modding.scssoft.com] for details.
@include "suitable_for_mod_cabin_a.sui"
@include "suitable_for_mod_cabin_b.sui"
http://pete379jp.s69.xrea.com/image/steam/Peterbilt_389_Pack_patch_04_01.png

Save (overwrite) "super_cool_ab.sii". It's done.


Activate this patch on the mod manager of the game.
You don't need to repack this patch (folder), just leave it. It is neatly recognized by the mod manager of the game.

This patch mod must be above my mod and other author's mods you have created patches.
My mod and other author's mods priorities are not a problem as long as they are below this patch.

For example:
1. economy mod
2. weather mod
3. Peterbilt 389 Compatibility Patch <== this patch
4. awesome interior mod <== other author's mod related to this patch
5. company texture mod
6. Peterbilt 389 Accessories Pack <== my mod
7. physics mod
8. super cool paint jobs mod <== other author's mod related to this patch


This patch is not dedicated to my mod. You can build it as your own patch, including other author's mods.

And as with my mod, do not forget to sell the related accessories before you delete this patch in the future.