These are implemented in the Adishila devanagari font 

https://adishila.com/wp-content/uploads/2020/07/Adishila.zip.

I notice that adishila.com also has updated Adishila and Adishila Vedic Font on their website, I don't have these but I presume that jihvamuliya and upadhmaniya are also part of these fonts.

 I can't comment on whether adishila.com's implementation is correct or not.

Harry Spier