When a Run-Time Composite Payload parameter is required, the parameter area changes to a grayed out edit box.  Unlike the other two types of input, you do not directly enter the parameter.  Instead, when a Run-Time Composite Payload Parameter is required, the grids check boxes become enabled so you can use your mouse to individually check all the "leaf" Authorization Definitions you wish to include in the payload (parameter). See the image below for an example:

Note in the example above, Authorization Definition #11 is the Run-Time Composite. We have included as "leaf" definitions for inclusion in the payload parameter definitions #3, #4, #5 and #9.  Note that the Composite Payload in the grayed out edit box is updated to reflect the currently assembled payload.  Note also that we have actually included in the payload a Design-Time Composite Definition which allows us to do even more complex activations (if needed).

You can not use any Authorization Definition which requires an implicit parameter as a payload item in a Run-Time Authorization Definition.  Specifically - you cannot use Change Expiration Date Authorization Definitions, Change Expire Period Duration Authorization Definitions, Add Allowable Executions Authorization Definitions and other Run-Time Composite Authorization Definitions.

You must click directly on the check box in the left side of the grid to select a payload item - not just on the row.