I checked on some customer messages that the customer is following the steps from help link bellow, to create FPN connections for Portal 7.3, and have the "ADD to My FPN Connections" option unavailable.
http://help.sap.com/saphelp_nw73/helpdata/en/d2/4fc11c3fef40d6a4a39b2bef85c550/frameset.htm
I have discussed this issue with a developer colleague, and the solution for this issue will be available on portal 7.3 SP2, but there is a simple workaround that solve the issue:
1) Go to NWA -> Configuration Management -> Infrastructure ->
Application Modules.
2) Use the search to find the producer_management module and select it.
3) Select the Web Dynpro Properties tab. You will see at the bottom the
property named ConsumerMode.
4) Changing this property to "true" should enable these options
5) Click on save button.
See the screenshot bellow:
result:
