Most modern editors nowadays have an option to switch on a "minimap" - an image along the right hand side of your editor which gives you a high-level overview of your source code, which is useful for quick navigation and code understanding. This is quite separate a concept to the code navigator.
This would be particularly useful for large scripts and packages.
does right clicking in the editor, then selecting Desktop->Navigator not do it for you?
Admittedly it's not quite the same as a minimap, but I think it's better. Especially in PL/SQL code as it lists the various procedures/functions etc in a package, for example.
I use the navigator, but like you allude to, it's not the same as minimap, especially when working on large PL/SQL packages. I also find the navigator refreshes a lot which becomes really irritating. It's not the refresh as such it's the way the invalidation of the navigator tree paints. It should be double buffered or maybe triple buffered, to prevent the obvious annoying flicking / repainting.
A minimap really does speed up coding, especially jumping around. It's one of those editor tools that has become invaluable in this day and age. I just think it would add value to TOAD.