Invoice customization for services - performance date, item list headings

ERPNext: v11.1.48 (master)
Frappe Framework: v11.1.43 (master)

Hello,

I am trying to integrate two informations into the invoice.

  1. Performance date (in Germany: Leistungsdatum)

  2. Change the header of Quantity to hour

2019-07-25_invoice_change_quantity_add_performance_date

Questions:

  1. Item Table:
    1. Where are the table headings defined?
    2. Is it possible to create a own template for services?
  2. Performance date
    1. How to link information from a timesheet, like the performance date to the invoice.
    2. Is it possible ot integrate a list with date and times of the hours workd?

I’d be thankfull for any hint!

Any Update??

Thanks in Advance