Are you tired of scrolling through 'endless' pages of different animal leather, chitin, scales, feathers, etc? Do you get upset when you want a leather bag made but instead get a chitinplate bag?
The following changes are what you are looking for. They are intended to remove all of the 'flavor' from leather, chitin, scales, feathers, shells, and a couple other things.
In the stockpile options for Leather you will only have the following items:
Dragon Scale
Suede
Netherbark Leather
Leather
Rigid Chitinplate
Rigid Shellplate
Rigid Scaleplate
Feather
Fur
Stomach <-- Was already in the list from, but lost within the huge list.
Chitinplate
Shellplate
Scaleplate
Bonerattle
Tough Leather
Studded Leather
Lamellar Leather
Those will also be the only leather options when specifying the material for leather uniform items for your military.
If you use Workflow, you'll have an easier time finding the particular leather type that you want. (Currently, most of them are all under a nameless creature). Just start typing the name once you have gone into the Creature parent menu.
NOTE: As I'm typing this, I realize that suede is still hidden under a nameless creature, but it is the first nameless creature in the list, located about 28 pages down the list.
There's a lot of files to modify, so make a backup of the RAWS before you do this. Using Windows, I just use Explorer to search for the particular string that I need to change. There will be a few extra files listed that don't have what I'm actually looking for, but there won't be any files that are missed. I'm sure other tools and editors can also accomplish this.