Customize theme: Always show tax column in invoice lines

In the new themes it is not possible to influence what columns are shown in the invoice.
I would like to always show the column taxrate per line.
Now it only shows the column taxrate if within an invoice 2 lines have different taxrates.
How can I influence this so the layout of the invoice is always the same?

Themes don’t support this. Themes are more about look & feel than adding new information.

But why do you require this? If all line items are the same tax code, then Manager will show tax code under total figure. That makes invoices more compact and easier to read without repeating the same information on each line item.

Some customers require this, however for the time being this is ok.