It would save you reading Makefile each time you are not sure what some option really wants to do. Ideally, it would point to a port name/it's pkg-descr or at least marking by colour/'*'.
Filling a PR so it would not get lost.
Permanently tagged default options would be nice too (as in ml thread with Kevin Oberman). It would help with those 'why I can't do/compile X while using non-standard OPTIONS and having already forgotten about it'. I think it clearly looks like a dialog4ports feature request now.
There is already a mechanism in place to describe what options do in more detail, it is to put the explanations in a file called pkg-help.
See make -c /usr/ports/dns/bind9-devel config
It tells you to type <F1> or ^E to see more information.
(In reply to Mathieu Arnold from comment #2)
Thanks, I've missed that, still, in my case I'm primarily concerned if an option pulls in another dependency or not, I think that's pretty basic stuff. Similarly, if it's a default or not. e.g. we now have '+' for previously unset ones, '*' could mark the ones pulling the other stuff and 'd' the default ones. It could look messy though, so there is a better way to do it probably.