Query Builder files (.qbw files) can be shared with other users, but both users must have identically named server registrations in identical locations within their Schema Browsers for the .qbw file they are sharing.
If one person has a .qbw file with a connection to "SQL Server 2000 .54" and shares that .qbw with another user, the recipient must have a registered server called "SQL Server 2000 .54" in the same place in their Schema Browser in order to successfully connect and use the Query Builder file.
If the recipient of a shared Query Builder File does not have the expected registered server in the expected location in their Schema Browser, then an error dialog will appear when they attempt to open the .qbw file.
If both users have a registered server "SQL Server 2000 .54", but one user has this registered server in a subfolder of their connections and the other user does not, the .qbw file will not open. An error dialog will appear explaining that the connection could not be found.
See how to copy server registrations from one machine to another machine for instructions on sharing registered servers between Aqua Data Studio users.