You can find all current navs at Category:Navigation Templates. The easiest way to go about new nav templates is to just copypaste the code of another nav and change all relevant parameters. If you are unfamiliar with wikicode you might have to do some reverse engineering to get the hang of it, but once you recognize the patterns it's relatively easy to edit.
As for finding all the items belonging to one mod, I have found looking at a mod's source code to be the most reliable, but there are also other ways of doing it. Some mods have creative inventory tabs. Many mods will occupy a specific range of block/item IDs which you can look at, although this method is rather fallible. So the other option is to disable all but the one mod which you are looking at, start up a fresh creative world and check which items are left available. It's easier than it sounds, really.
The following mods do not have a navigation template yet:
Advanced Machines(x) Advanced Solar Panels(x) Assembly Line(x) Atomic Science(x)
- BackPack Mod
- Diamond Buckets
Electric Expansion(x) EnhancedPortals 2(x) Equivalent Exchange 3(x) Extrabiomes XL(x) Fluid Mechanics(x)
- Furniture Mod
- Logistics Pipes
- Metallurgy 2
Natura(x) Nuclear Control(x) OmniTools(x) Petroleum Generator(x) Soul Shards(x) Thaumic Tinkerer(x) TubeStuff(x) Wireless Redstone CBE(x)
Please post here if you have made any progress on any of these navs! Thanks!