How to customize math fonts globally in a document

I am aware that it is possible to use with primitive to change the math fonts in a local fashion. I wonder how to do that globally over a document? Thanks.

It seems to me that one can choose it in the menu: Document->Font->Mathematical Font

I tried this. It seems that, if I select “Mathematical Font” there, and choose a font, then the font for the main text is also changed to that.

This is the test I did:

Document with Roman text font and Roman math font:

Document with Roman text font and Dejavu math font:

For me the math font is in Document->Font->Advanced... (with Edit -> Preferences -> Complex actions -> Through popup windows)

You can also set this in the preamble

 <assign|font|math=Stix,Cantarell>

Thanks, this works. However, it seems that the options for math fonts are very few. I don’t see, say, TeXmacs Euler Roman.