Flex entity 1:1 cardinality with BP_Header is read only

Hi all,

We have created a custom flex entity with three fields in BP data model with a 1:1 relationship with the main entity BP_Header. We followed the below document to configure the same:

http://a248.g.akamai.net/n/248/420835/1de145bfc626ae6424e2d794db15207c3d2881c8cad41e5013831eefe8efc98a/sapasset.download.akamai.com/420835/sapcom/docs/2015/07/a6fef25d-5b7c-0010-82c7-eda71af511fa.pdf

However after adding the fields in the custom entity to the UI, the fields are read-only and we are not able to edit. Please help to know how to make these fields editable in the UI.

Regards,

Ponraj M