Learn how to change the parameters of standard connections within a custom connection instance without impacting the definition of the custom connection.
You can tab select a nested standard connection within a custom connection. Click Modify| Structural Connections tab 
Connection panel (Modify Parameters) to open the specific connection dialog and change parameters. The nested connection is changed, but only for that specific instance of the custom connection type.
If a custom connection contains steel parts (like plates, bolts, and welds), some part parameters are available and can be changed separately for single instances of a custom connection. Tab select sub-elements of a custom connection to view their parameters in the Properties palette.