Creation of Action Validation is not possible

Hi Experts,

I wanted to create Action Validation in my generated CDS View based BOPF BO,

but it is not allowed in transaction /BOBF/CONF_UI.  It can be opened only in display mode.

(Figures 1. , 2.)

I tried to use transaction BOBX instead.

Edit mode is allowed here but Create Action Validation is missing from the context menu

(Figure 3.)

Is there any prerequisite to create Action Validation in this case? Or any other idea what's wrong with it?

Regards,

Laszlo

Figure 1. (transaction /BOBF/CONF_UI)

Figure 2. (transaction /BOBF/CONF_UI)

Figure 3. (transaction BOBX)