I have created a low bookcase where the animations for high and middle would not be needed:-

After creating the bookcase, I saved a copy of the SimPE file, then deleted all the examine/put/get for high and middle in the animations resource; followed by a "Fix Integrity" and save.
When tested it in-game, Sims still examine and get the book on the high shelf.

Is there some way to disable these functions that are not required?
Is it possible to adjust the height to make them all the same i.e. the low option?

Thank you in advance for any help you can offer.

The animations are usually located in the BHAVs + possibly some other resources (not entirely sure how it's best to edit them, though).

The anim resources are just the actual animations, and they're not used in the object as far as I know. I think the object still uses ingame animations unless you tell it to do otherwise.