Table and Field for Text delivery to Proforma invoice

Hi Experts,

I have created successfully Header text to flow to Proforma invoice header Text.

Now I need to understand which filed from delivery to proforma invoice is flowing? STXH is having Text ID text object VBBK are available.

Let me know which Table/field relates for VBRK data? As I could not find delivery table in invoice.

Appreciate for early help.