The Neptunian Trojan is just that ... so far it's unique!

There are 'Earth Trojans' too, but as the orbits they have around the Lagrange points are rather extended, this is not a good description.

Better is the concept of resonance; all Trojans are in 1:1 resonance orbits, Pluto (and plutinos - there are several) are in 3:2 resonance orbits (with Neptune ... I think; I'm going from memory).

The EKB (Edgeworth-Kuiper Belt - everyone forgets poor old Edgeworth!) is indeed a true 'belt', and possibly a much more massive (and interesting) one than the familiar one (between Mars & Jupiter). It seems the EKB has a rather distinct outer boundary - why? And are all the SDOs 'merely' scattered EKB objects? Or perhaps (some) the remnants of older, earlier, distinct belt?

Then there's the question of the Oort Cloud - how many 'belts' does it comprise??