I'm using LyX on Windows 10 with AMSthm module and need to make some changes to the environments. (Including: 1. making theorem not italics, 2. adding new environments like "Challenge" to appear also on the drop down menu, etc.)
Similar questions appear to be have been asked already, e.g. here, but I cannot find a useful answer.
It seems I should define my own module? (or Layout?)
If so, where do I find pre-existing module file, and where do I place the one that I edit?
In particular I can't find anywhere the file "stdlayouts.inc" mentioned in the answer above.
Thank you.