Yes, you'll need to create the open/closed configurations in the sub-assembly as well in order to get it all to work well in the upper-level assembly.
You might also look at using DriveWorksXpress (located under the 'Evaluate' tab on your command manager).
Thank you! I have never used DriveWorksXpress before but I will have a look at it when I get some free time!
If you want to control the position at the parent assembly level - one alternative (I don't recommend this for a default configuration as it is less stable) is to make the sub assembly Flexible.
At the sub assembly level you would have an "Adjustable" or "Flexible" config. Then instead of a fixed position you use something like a Hinge mate or Limit Angle, or leave rotation unconstrained. At the parent assembly you can then mate the door into whatever rotation position you want - and adjust it with an Angle mate or something.
If you don't need to check various positions at the parent level then I'd go with the more solid approach of fixed Open and Closed configs.
Recently I've started tagging mates - meaning I'll prefix the default name with something like "Suppress to Move-Coincident1" or "MoveMate" and then I can filter for that to find the mates that control movement. Useful for temporary changes.