To add icons from other mods I use FastStone Photo Resizer
The preset I use is included in the "_patches" folder

To use the preset select 'Use Advanced Options' at the bottom right, then click 'Advanced Options'
Select 'Load Options from File' and navigate to the preset. Once the preset is set you can use batch convert

Make a copy of the panels folder you want to add to this mod, that contains the icons you will need to resize
Select the copied panels folder and click 'Add All'
Set 'Output Format' to PNG, uncheck 'Output Folder' and 'Ask before overwrite'
Click 'Convert' and wait for it to resize all of the icons
Once it finishes you can move the newly resized panels folder into the root directory of this mod (where there is already a panels folder)
DELETE 'modfiles.txt' OR YOUR CHANGES WON'T BE APPLIED
That's all you do to add support for a mod

