Fiori Elements: delegating action of 1:n associated entity on object page to parent object?

[Robert_Schulte]

Hello everyone,

i am evaluating the capabilities of Fiori Elements atm - is there any possibility to do this?

Background: imagine, there is some root entity for which you need to persist the (1..*) "involved business partners".

One child entity (composition) of the BO then would be "involved business partners" e.g. having key of parent entity and business partner id. 

As there is no possibility to have value helps returning multiple keys for that case, an idea would be to also associate the available business partners with the root entity - the data could be displayed as lineitemreference in the object page.

Via annotations one usually can define custom actions which by default invoke actions on the displayed entities (business partners). 

Is there an option to delegate defined custom actions to another (related) object while supplying the selected keys? In my example, it would be the "parent", which then would have need to have some action like "add these business partners as your child entities".

I was trying to find out, what options exist or might come in the future regarding #FORACTION but unfortunately, the documentation is not complete.

Related: can sb help me regarding the syntax for "dataaction"? Usually i't's the action on the displayed entity. But i also saw "BOPF:" (meaning is clear), "PUSHDOWN:" (no idea - used in examples but not documented - e.g. "PUSHDOWN:STTA_C_MP_ProductCopy_new_supplier") and some syntax which seems to fully specify RAP object plus method, also used in examples but not documented (e.g. "com.sap.gateway.srvd.sadl_gw_appmusicdr_definition.v0001.BREAK_UP"). 

Otherwise: any idea, when / if value helps with multi selection become available for Fiori Elements 1:n entities?

Best regards,

Robert