A lot of queries in this space revolve around POWL based Inbox and how it can be configured to be used in MSS. I have uploaded a document which gives a step by step guide for configuring the POWL based Inbox for MSS.
Here is the link to this document –
In this document I have tried to explain with a scenario where one would like to bring a workitem(custom workflow) in POWL inbox and configure actions. There is also collection of useful links from help.sap.com towards end of this document.
I hope that this it helps in understanding the configurations for POWL Inbox.