Time-dependent link categories
Because I like to track things over time the way I'm using PB link categories are often determined by time. E.g. when linking persons to projects I constantly have to manage 3 types of link categories manually: future, current and past. The same approach is used in many relationships: person to person, person to department and so on.
It would be much easier if PB would offer two additional fields in the link properties: start and end. Based on these two properties one could define up to three dependent link categories. PB would then be able to change the link category over time.
This is not really my original idea. It's actually taken from a discontinued tool called InfoCentral from WordPerfect.