Hashtags are an incredibly powerful feature, as they allow for the kind of qualitative data analysis found in programmes like MaxQDA, NVivo, and Atlas.ti. i.e. You can tag each individual quote in your research materials, and then retrieve those quotes using search filters.
BUT, in their current form, hashtags are just a massive list with no hierarchy or differentiation. This makes things messy when working with hundreds of hashtags, as you end up with a completely disorganised list.
I would recommend two features:
hashtag groups: folders that you can add hashtags to.
sub-tags: a hashtag within a hashtag. When searching/filtering, there would be an option to “Include Sub-Tags” - e.g. Let’s say you have the hashtag “Philosophy” and the sub tag “Plato”; if you search for the hashtag “Philosophy” and select “Include Sub-Tags”, the results will include quotes tagged with “Plato”. That way, you don’t have to add a large number of hashtags to each quote; you can just add the lowest sub-tag in the hierarchy.
For an example, see the Keywords feature in Scrivener, where you can nest tags within a hierarchy: