Font not appearing in JSON File for me to Edit

Good morning All, 
I've got the latest Desktop version of Power BI and I wanted to customise my fonts for a custom theme, however I've saved the theme json file, but when I open it up in notepad, from all reports I should see an area something like

{"fontFace:": xxxxxx"}

However I cannot find anything resembling this in my JSON file

{"name":"CY23SU02","dataColors":["#118DFF","#12239E","#E66C37","#6B007B","#E645AB","#4A2D75","#1AAB40","#10433F","#3599B8","#DFBFBF","#4AC5BB","#5F6B6D","#FB8281","#F4D25A","#7F898A","#A4DDEE","#FDAB89","#B687AC","#28738A","#A78F8F","#168980","#293537","#BB4A4A","#B59525","#475052","#6A9FB0","#BD7150","#7B4F71","#1B4D5C","#706060","#0F5C55","#1C2325"],"foreground":"#131312","background":"#FFFFFF","foregroundNeutralSecondary":"#6C6966","backgroundLight":"#E5E0DA","foregroundNeutralTertiary":"#ABA7A2","backgroundNeutral":"#C6C2BE","tableAccent":"#118DFF","maximum":"#4A2D75","center":"#1AAB40","minimum":"#E645AB","bad":"#E66C37","neutral":"#6B007B","good":"#12239E","visualStyles":{"*":{"*":{"background":[{"color":{"solid":{"color":"#FFFFFF"}},"transparency":53}]}},"page":{"*":{"background":[{"color":{"solid":{"color":"#FFFFFF"}},"transparency":100}]}}}}

Any help would be greatly appreciated!