Arpit,  Skuid only supports standard field types at this point.  Salesforce has bent its own rules here by creating a text field that also includes picklist values.  This is not one of the field types that Salesforce offers - and therefore we are not supporting that complex interaction in our builder. 

We will take your note as a product development suggestion and put it in our issues list.  Both for supporting the Subject field of the standard task object, and also allowing text fields to have predetermined values. 

PS - good to hear from you again.  We missed you.