You can Script a database sign-on. This is mainly designed for use with Batch Mode operation of AQT. However, in normal AQT operation you can run a script with a number of Connect functions. This can be used to sign on automatically to a number of databases without having to go through the sign-on dialog. Scripting > Connect function gives more information on this.
You can automatically connect to a database when AQT starts by clicking on the database in the Recent list then selecting the Connect to this when AQT starts option.
Within the Database Explorer there is an option File > Reconnect to Database. This will disconnect you from your current session with the database, and reconnect you to it. This option is useful if your database session has timed out or been disconnected for some other reason. The Reconnect option allows you to quickly re-establish the database connection.
AQT also has the ability to auto-reconnect to a database when it has detected that the connection has been closed. This option is configured on Options > Technical Parameters.
Information on your Datasources is held in the Registry under key Software\ODBC\ODBC.INI. For System Datasources these are in HKEY_LOCAL_MACHINE, for User Datasources these are in HKEY_CURRENT_USER.
While it is not recommended practice, it is possible to manipulate these entries using regedit. An example would be copying a set of entries from one machine to another. This will only work if the relevant ODBC Drivers have been installed on the target machine, and the database client has been installed and configured.