ABAP RAP functions - how to default values to a drop-down in an abstract entity cds

I have an action button in behaviour definition I have defined the below

This below example doesn't have any Ui5 coding

storePut is function import

action ( features: instance) storePut parameter D_StorePutAbsEn result [1] $self

D_StorePutAbsEn is an abstract entity cds which opens the dialog having all fields like

Key F1

F2

I want to default a value to a drop-down for field F1.

Is there any annotation in cds or annotation in xml by which a value can be default to a drop-down inside the dialog.??

Any example how to achieve it .?