How do you set the default font of web-based iCloud Mail in Chrome on Windows 10?

I predominantly use the webmail version of iCloud Mail, loading it into a Chrome window running on a Windows 10 HP laptop. At some point in the past, the default Mail font in new emails changed permanently to the awful Comic Sans. I tried then to change it to a better font, but there is no way to do that within the online iCloud Mail program or the desktop iCloud application for PCs. The "iCloud User Guide" is sadly useless. One method of changing the default that I found online says if I change the font on a new email and send it, that will reset my default font to the most recently used font. This doesn't work for me.

I am pretty tired of changing the font size and the font on every single new email I send. My default font used to be Helvetica and somehow it changed to Comic Sans by itself, so clearly setting a new default font is possible, but it seems Apple hasn't included the tools to do so in a browser window.