Substance Designer Community Wiki
You are able to add other files
inside your preferences you can update
Navigate to the application on your C drive
If using Steam
C:\Program Files (x86)\Steam\steamapps\common\Substance Designer 2018\resources\templates
Or here
C:\Program Files\Allegorithmic\Substance Designer 2018\resources\templates
You then want to copy the setup substance to this location
The order is sorted by adding a ##_ at the front the lower the number the higher it is placed.
Here is one I have already made if you edit this substance then you will change the preset
00_Template_MR