Easy way to do diagonal belt transport systems?

[FizzMan]

It's a real pain in the ass getting them to go diagonally well XD
Is there a good mod or some keybinding that makes this easier?

[Fel]

Your best bet is to not do diagonals and instead do two straight.

But if you really want/need a diagonal, you can first lay down all of the ones in one direction (for example horizontal), then all the ones in the other direction (in the same example, vertical).

[Dobbelklick]

Don't force the square through the round hole. :)