Design a table of items with many features; how to group those features
Up front disclaimer: I am a SQL DBA, so exact solutions may differ.

Two approaches that I have seen to this. The first is to ask if a single person can be an admin for more than one store. Can Paul Smith have store 27 and 19? or just one? If that is the case, then I would add the needed fields to that persons' profile.

A second way of approaching it is to have a join table that would look like this:

Join_ID |  Admin_ID |  Store_ID | Admin_Type_ID

This way would be a many-to-many situation, where a single person can be assigned to multiple stores, while a single store can have multiple admins of the same or different types. You could also use this to have one person be a general manager at one store, but a network admin at another.

The overhead for this should not be too different than anything else going on in the database, and should only take a few extra minutes to plan out how the stored procedures would read and write to it.