This is a bit fussy but if you're anything like me, you frequently feel a grain of frustration - when on iOS - that in order to type a hashtag, you have to press two buttons before the hashtag button appears. When applying several tags to an individual note, this is a bit annoying.
So I went to 'text replacements' in settings and set it up so that when I type 'hh', the hashtag appears. It's a very small time saver, but it might help you!