Hi,
Tropy is designed with the expectation that you will divide up your letters into individual items. When you put all of your documents into one item, there’s not an easy way for your brain to process them as individual letters even if you could tag them separately. The point of the metadata templates is to allow you to add biographical/geographical information to individual letters in a way that’s coherent and consistent. Tagging really isn’t the best way to go about this, as it’s purposely freeform and you really do want consistency in your biographical details. Bulk metadata entry ought to make much of the process of adding these details pretty straightforward.
This video we created about letterbooks might be useful to you in thinking through how you want to break up your items, even though your specific situation might be a little different: https://vimeo.com/310153280.
Please let us know if you have further questions.