As I understand it, Markdown should work, but for me it does not (also see my post Again: Purchase Invoices and Reference field). I just upgraded today to Manager desktop edition for Windows, version 15.7.4, hoping that would solve the problem, but . . . no.
As you can see in the pictures I enclosed in my previous post, Markdown does not work in my custom field, here with the title ‘Link to scanned document’. So again: why is Markdown not working for me, even in custom fields?
Invoice - Internal information field and Custom Field