Usually a drawing layer (node) contains all art elements you create in it (drawings substitutions): in your case these 2 different arms.
Alternatively the drawing layer may have keys (animation keys for position and rotation, etc). So you can bring the same arm substitution f-1 and use the transform tool to place it where you need. That creates a new key (if you have pressed the “animate” button). Some times these keys are not in the drawing layer but in a peg, but the principle is the same.
All these keys won’t show up in the drawing substitution.
Imagine you have arms f-1 and f-2. If you want to have an arm like the f-1, but rotated as f-3 you can select f-1. Select “duplicate drawing” as f-3. Modify the drawing with the BLACK ARROW TOOL, NOT the transformation tool. and voila. Now you have 3 drawings in the substitution list. f-1 and f-3 the same but rotated.
However it is not very advisable to do this. It is much better to use keys.
If you want to store positions (not only drawings, but the position and scale, etc) to reuse them later, then you use a template. Templates can be created by dragging the desired drawings and keys into the library and assigning a name. You can later on use the thumbnails to identify the right arm and drag it back into the timeline on the desired frame.
Just notice that templates and drawings substitutions are different things. As far as I know, drawings substitutions have vertices and color information and a pivot, but nothing about where to place them in the scene as such.
Hope this helps,