Created attachment 150110 [details]
Its impossible to change the formula font type.
Can not confirm on Windows 10 Ent 64-bit en-US (1803) with
current master/6.3.0alpha0+ nor with
Version: 18.104.22.168.0+ (x64)
Build ID: dfa1f1f872c418e89757a3985979b79e94c12fcc
CPU threads: 8; OS: Windows 10.0; UI render: GL; VCL: win;
Locale: en-US (en_US); UI-Language: en-US
The Modify element Split button selects element to assign font.
The Font selections made, are then available in the formula element Drop list.
Working correctly on Windows builds.
Thanks for reporting this issue.
This is a duplicate of bug 124028 and it's fixed in LibreOffice 6.2.2
*** This bug has been marked as a duplicate of bug 124028 ***