You need someway to edit .yaml files, "Notepad++" is good program for that.
You also need a way to open .zip files, "7zip" is a decent option.

For quick editing directly from 7zip, open any zip file.
Then click Tools -> Options... -> Editor
Then click the 3 ... next to the editor box.
Locate and select "notepad++.exe" and your good to go.
(I did this a LONG time ago, and forgot how, in any case, here you go.
Thank the comment section for reminding me.)

Now your set, next step, editing.

First, you need to have a save game, so go play for a bit, once you have a bit of downtime on the world map, save the game, and remember to give the save game a simple name. Like "Clown soup". For instance.
It's unique enough that it's easy to find.
(For this guide, I'll assume you gave the save game that name.)

Navigate to " C:\ Users\ ****\ AppData\ Local\ PhantomBrigade\ Saves\ Clown Soup ".
Open the "Content.Zip"

The "difficulty.yaml" Is rather self-explanatory, but let's edit at least 2 values here for our benefit.
Change the following settings to 99.0:

• combat_salvage_budget_defeat
  
• combat_salvage_budget_victory

This'll allow you to take all items from the battle field, either when you get defeated or win.
(This does NOT work in the first sector, the tutorial sector, as it's hardcoded.)

Save the file and close notepad++, 7zip will then ask to update the "content.zip", just select yes to this.
If this does not work, you should be able to just extract (drag&drop) the file, edit it, then import (drag&drop) the file back into the zip file. (just remember to delete the extract file outside of the zip, the file inside the zip, game needs that one.)

Next we gonna set our supplies/salvage value to 10.000 (MAX value without modding.)
Open "content.zip" again and then open "OverworldEntities" folder and look for "squad_mobilebase.yaml" (usually at the bottom), and open the file.

Scroll down just a little bit till you see something like:
(usually around line 60-some)
(I replaced the numbers with # in this example, as the values will most likely be different from my game to your game.)

Now set "Supplies" value to 11000 .
(Seriously, there is no point in going nuts with a lot of 9s, the game caps the amount at 10.000.)

For Uncommon materials, add "components_r2: 110" under battery.
For Rare materials, add "components_r3: 110" under battery.
These 2 materials are capped at a mere 100. Sadly.
A mod might be able to alter this max value to something like 9999 or what ever.

Save the file, close Notepad++, If using 7zip, it should now ask you if you would like to update/overwrite the edited file, just click yes.

You CAN update "metadata.yaml" to reflect the new amount of supplies you got, but there is no point.

Done.

There might be more fun things you can edit in the save file, such as the bonuses the weapons / mech parts has.
Once you do, just save game edit yourself to 10k of each, now just go upgrade your base.
Then go build some rare body parts for your mechs, and kick some cake or something.

You'll be zipping around the map in no time. And hey, if the overheating stuff is annoying, just change the difficulty settings to some outrageous values to benefit yourself, and have more fun.
Setting overheat to only 10% is effectively the same as turning it off. You can rapid fire and dash about without worry of overheating. Ever.
Go experiment :D

This does not seem to disable achievements either, sooo... have fun?

I know I am having loads of fun!
Ciao for now...

My discord server: https://discord.gg/pWUcg3NUpm

Made 2 mods:
Huge Resource caps[www.nexusmods.com]
and
Extended Difficulty[www.nexusmods.com]
Will try make a mod that makes you start with 50k of the 3 resources when starting a new with the "quick start" option.

Hope that some people can make use of this video.
Sorry if I sound passive aggressive or accuse people, not my intention.
Maybe i'll remake the video when i'm not tired.
(Note the time in the bottom right of the video, it's 5 am when I made this video...)
https://youtu.be/9d5DDf2hvmk