When an invoice is selected in the list on the Invoices folder, if there is history on file the drill down button will enable on the left hand side of the screen. Clicking that button, using the hot-key Alt-Z or double clicking the invoice in the list will pop up the A/P Invoice History Inquiry where you can see the detail of the invoice. Since you are using ABC demo data, try vendor '01-AIRWAY'. Invoice 678AB478943 was posted from the P/O module (if that applies to your situation) and 0000106145 was posted from A/P.

Thank you for the quick response Steve !

I understand now how to drill down to get into invoice history. If the option is grayed-out, it would mean that no information is available and the the invoice is kept for historical reasons ?

That is correct, if history is not on file for the selected invoice the button will be disabled.