Is it possible to store information in a Revit file that is not directly associated with revit objects? The purpose of which would be for an add-in to access the information and add it to Revit items as they are created.
This would be similar to named dictionary objects in autolisp.
Does Revit have similar capacity?
I doubt that this can or should be done, what i would suggest is just have your addon read this information when it is needed from the source.
Yes. Key schedules will permit this to some extent, and are openly available to all users. However because they are open to all users they often get deleted or edited by a well intentioned but uninformed user. Fortunately they are also easy to re-insert if a user accidentally deletes them via the insert view from file command.
For a more robust method you can look into the use of extensible storage in the Revit API. This is not for the faint of heart though as the methods are not as simple as you’d think, and the scope can be detrimental. The Pack And Play package in ick age manager will actually place DYN file’s into the RVT for easier distribution. The code was written entirely with Python so others could learn the mechanics. Feel free to start there but be sure to change your GUID or your schema may be overwritten by mine.