I’ll frrely admit that my first foray into Bookends formats left me anxious but it’s easy - don’t be put off by ill this inputs. In this use we’re simply reading fields verbatim out of fields like note, so no gnarly author name wrangling or the like. What looks baroque at first encounter in Bookends is actually elegant once you find the need for a not default setting (and the dev is responsive to ‘missing’ things - often it’s just that no one ever had that need before).
Aside from making new formats (or modifying existing ones) the basic use is this. In Bookends Forma’s Manager tick any/only the format you want easily available in the main app UI (300+ in a list is overkill!). Then either in the Bookends bottom status bar or in the Bibliography export dialog (menu: Biblio ▸ Bibliography…) a pop-up lets you (re-)set the current format to be used for any export-related feature.
So, once the format’s made and ticked, it’s a pop-up menu away from use.