Inbound Plug in standard SAP (create as an interface)

Hi All- I have a standard SAP component that I create an Inbound PLUG at the window level, I'm using that component (standard SAP) in another component (custom) but I don't have access to the inbound plug that I just create in the standard SAP because the check-box for interface is not "CHECKED".

When I try to enhanced the standard SAP the interface check-box disappear, how can I check that check-box interface box?

How I can make my custom inbound plug accessible globally?

thanks!

Jason PV