You can only lighten a Pantone color using percentages. In a printed project these percentages make the dot of the halftone smaller or bigger.
You can previsualize it on your software, which will simulate making it lighter.
The only way to darken a color is by using another darker ink, or at some extent using a complementary color, so you now have a duotone.
You can simulate it using multiply blending mode on the software you are using, but it is only an approximation. In the simulation, you can "cancel" a color making it black, in real life you can not achieve this, that is one reason to add black on a CMY print.
A pallet can be the result of combining two perpendicular gradients.
But again, it is only an approximation.
identify related shades of a Pantone color
This is relative. Orange can be related to yellow, they are different inks but both are "warm".
But comes to my mind a post I wrote some time ago, about not using a light Pantone color, but using one similar at some percentage, and now you have the original color as one more "darker". Take a look: Printing photographs when job is a 2 spot color job