I am not a coder so I can’t help much here but I know that all field and its content formatting in Anki is done in CSS or html. There are plenty of free tutorials on the Internet. For example:
There is also add-on that allows to edit in external editor but I don’t know of editor that could change format in html.
Here you have official support thread where you can ask for help.
Note that sometimes it is important to add !important to override other settings for example field styling.
font-size:36px !important;