As @Frederick_Law stated, you have to create a Positional rep at the assembly level, then use the positional rep of the sub-assembly.
For instance if you have a cylinder, and that cylinder sub-assembly has an Extented Positional rep and you want to use that extended rep in the upper level assembly, then in the upper level assembly create a Positional rep called "extended" or whatever you want. Then Right Click on the cylinder in the assembly > Override > Component tab (there by default) Check the Positional Rep Check Box and choose the extended representation to use.
This will set that particular representation to be used for the current assembly representation.
When you go back to master the cylinder goes back to the closed state. Double-click on the extended representation, the cylinder extends.
Then in you drawing of the upper level assembly, you would use the overlay command to add the representation to the drawing.
Hope that helps!
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