gConnectionManager allows editing connections in application configuration files.
gsqlcmd edit /user
Also, you may open the desired configuration file using the gConnectionManager File, Open menu item.
Here is a configuration file example:
Check the leftmost column to activate or uncheck to deactivate the connection string.
Click the ... button in the rightmost column to edit the connection.
Here is an example of selecting a connection provider:
Here is an example of connecting to a database: