MDGC Custom entity STA<->API Mapping problem

Dear Experts.

I'm trying to enable a custom uibb / entity under Company Code section.

I performed ( I think ) all the steps described here:

https://www.sap.com/documents/2015/07/d6928e5d-5b7c-0010-82c7-eda71af511fa.html

I can see my new UIBB, however I can not map data to staging area, because my custom entity doesn’t show up In [MY_HANDLER]~MAP_DATA_2STA.

While debugging I only see BP_CENTRAL and BP_HEADER entities, however the sample code ( from tutorial above) suggests there should also be "my" entity :

(…)
CASE iv_entity.

WHEN 'ZSECRET_N'.
(…)

I've also noticed that the GT_ECC_EXTERN_DB is empty and I assume it should be not ( there is a loop at GT_ECC_EXTERN_DB in a sample code).

Any clues?

Thank You.