Current syntax is inspired by GitHub search. The concept is different from Evernote. Indeed #tag syntax would be nice though, I’d prefer the obvious syntax.
The easiest way to filter notes with particular tag is to click a tag label on the editor pane.
I guess the problem is that I rarely use tags to filter notes. I use it just for annotating sub topics with a few tags like severity. So I didn’t make the app to work that way as you wrote.
This would be a discussion:
I guess you have a lot of tags. And tag searching would be nice for those who have many tags.
However, unlike Evernote, I would encourage you to reduce number of tags to manage.
I do have a lot of tags in Evernote but most of them have only 1 or 2 note(s). And I rarely use them.
It makes sense Evernote supports tag searching because you can store notes about various topics to it, from travel plan to business idea.
On the other hand, Inkdrop is specifically designed for taking notes regarding programming things.
Of course it depends on what kind of work you do, how many projects you have, and a personal preference.
But yet I would think if you have many tags that require searching to find, you have to clean them up.
And if you have a lot of notes that require filtering with tags, I recommend you to make sub-notebooks.
Since tags are very abstract, you can use it in various way.
Inkdrop would encourage rather managing fewer tags than doing a tag-intensive management.
It has to be opinionated in order to keep the app clean and simple.