Quoted item subform setup button missing to add back unused field. (Zoho CRM professional edition)

Quoted item subform setup button missing to add back unused field. (Zoho CRM professional edition)

With Zoho CRM professional edition, understand that we couldnt further customize subform.
But i notice there is no setup button for me to add back unused field that i accidentally removed (Tax field). it doesn't appear on left panel unused field as well.
Is there any method to add it back that im unaware of?

Unsure this setup button just removed recently or it also being removed since early days.
Quoted Item subform No Setup button


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