Any simpler guide to creating a working tagnavi_custom.config?
Anyone's welcome to correct me, but I don't believe there is...no.
This guide *is* fairly simple, but I guess it could seem daunting to some.
Use that link as a reference, but if you get stuck it may be better to pop into #rockbox on IRC and see if a helpful dev/user can offer you a "blow-by-blow" description on how to achieve your desired effect.
It's like riding a bike, it seems impossible at first, but once you learn how...well, you get the picture.
[St.]