Sorry, it's unlikely we invest time to implement themeing in WinSCP.

I love SCP a lot, I just find the interface very dull. I know you guys don't intend to create and manage themes, but it would be awesome if you could create UI assests that can be altered to make our own community templates. And of course, these assets should not be overwritten by the future updates. This way you guys can transfer the creativity part to us to make our own buttons, crazy theme colors, etc. to share between us :)

Thanks for reading! Have a wonderful day.