Hi Inukshuk & thanks for your speedy reply.
From this, I understand that the data types currently supported are date (YYYY-MM-DD), integer, and string - these are the main ones that I would need and I now understand their purpose so thanks.
Can you also comment on the other part of my question about how vocabularies work?
E.g. According to the DublinCore specs the property dc:type has set values (‘Collection’, ‘Dataset’, ‘Event’, ‘Image’, ’ InteractiveResource’, ’Service’ etc.) but I am not constrained to only those values when I enter a value in the Type metadata field.
In this example, if I start to type a value (e.g. “Im…”) in the Type field, I was half expecting that the only autocomplete options I would be presented would be from that vocabulary (in this case ‘Image’) but that is not happening.
Am I missing something?
More generally, you and your team are doing a great job - I’ve been accumulating a lot of information about 4 interconnecting stories that peak in Australia in the 1880s and was finding it increasingly difficult to keep the information organised and accessible - Tropy is doing this brilliantly!! Its a great tool and I particularly like the user experience, it is intuitive and fast, with everything organised where you would expect it to be.
I do like your proposal to look at a more sophisticated date widget. I have some material that I can only place to the approximate year (let alone month or day), so something that enables that ambiguity to be captured, while retaining the ability to list material in date order will be great (I guess the open question is what estimated date is used when a range is provided - I started using 1 January as not a lot happens then 
)