Thank you, Martin
Here's a screenshot showing WinSCP UI next to another program I'm running just to compare font size:
I read the advice here on the forum how to increase font size, and from my understanding the steps provided from the link in your signature achieve the same results. Basically, changing font size through the windows settings is an OS tweak, which I already did by the way as I'm using an UHD monitor. What I'm missing is the option to further customize the fonts in WinSCP itself.
Since I'm using a second monitor which is a HD 1080 screen, I run WinSCP on that monitor and I'm fine. Only I wish it was possible to have larger fonts for better reading on UHD screens and not-so good eyes anymore like in my case ;)