Inventory items in NIF-file have parameter "BSInvMarker" which have fields "Rotation X", "Rotation Y", "Rotation Z".

How to understand numbers in those fields to make nice rotation of my own item in Inventory ?

(I tried many combinations, but always got weird rotation of an object)

You need to be in another forum. That would fair better in the Mod or the CK forum. Ask a mod to move this for you.

Maybe you are right, "Creation Kit" topic is more suitable for my question (i thought it was for CK or Papyrus only)...

So, if moderator of this topic read this thread, please move it to "The Creation Kit".