Hi,
AFAIK the settings in the Drawings in fusion are based upon the relevant ISO and The United States National CAD
Standard (NCS) and possibly the UK AEC Standard. If it isn't a standard in any of those then I don't think you can
actually create a Custom Standard. You might be able to create a Hybrid of those standards but the idea is that they
are STANDARDS so everyone uses them and understands them.
You may be able to modify the drawings after you have created them in other software to get custom Drawings, but
the intent of Fusion is to be a Tool that uses the Standards wherever possible so that it is easy to change between
the various Standards. Take measurements for instance. The basic distance measurement under the hood of Fusion
is the ISO millimetre mm, but you can switch between mm and inches easily and more importantly ACCURATELY
with a couple of mouse clicks. Even other metric measurements like the metre m, fusion treats as 1000 mm. Also
American Customary Units or Imperial Units like Feet are all measured in mm and then converted.
I have not tried it but there are other tricks in Fusion to convert between various Standards and so there may be a
way to also do it with Drawings, but there is only so much flexibility that can be built in without going overboard.
The number of thread Standards alone is a nightmare.
I think you will be out of luck with Drawing Standards. Fusion uses the most commonly used and agreed upon
Standards to be compatible with other software and to meet Industry expectations.
Cheers
Andrew