Tactics on diagonals, do they exist?

If you like to play tic tac toe, then you already know.
No I went skydiving and ate some mustard and now the diagonals fell off a cliff
^^^^^^^

I'm going to give you the benefit of the doubt and assume that you're not a troll.
A lot of people already beat me to it, but just to reiterate: "bishop tactics" is a very broad category and includes a wide range of tactical themes like: pins, forks, skewers, discovered attacks, clearance sacrifices, desperado, mating nets, smothered mates, etc.
You have to study each of these tactical themes individually. You can't just look for any puzzle involving a bishop move.
And even if you could: that would be pointless. You'd already know what piece needs to be moved, so what's there to solve? The whole point of a puzzle is that you don't know what piece needs to move. You have to work it out yourself.

Lol sure a bishop can be in a position where it's forking, but that can happen only in two moves at least: first you attack something, then won't take it but move along the same diagonal (keeping the ongoing attack) and now attack something else. Or get a second attack by discovery. So, you can't actually play a one single move that goes from bishop attacks nothing worth mentioning, to "now bishop attacks two valuable targets by a fork!". Well, unless you count attacking north-west and south-east a "fork" (I would not eat with it)
Yeah I count an attack north-west and south-east as a fork.
It's not an ideal fork to eat with though...
If you like to play tic tac toe, then you already know.
No I went skydiving and ate some mustard and now the diagonals fell off a cliff