Tags are actually great, they are kinda like labels/mailboxes in Gmail, or albums in say Photos. And can be really useful combined with either smart folders or saved searches.
Folks would find them most useful when they have a set of say source files for a writing project. Some photos, text, email messages, etc. But all the sources are already in separate folders, and can't be moved (since a file can only be in one folder). But if you tag them with "Xproject" then a smart folder will "hold" all those files without having to move them outta folders, without having to replicate them, and without having to fuss with symlinks, aliases, etc. And Spotlight searches can find them easily.
It's kinda like using albums in your favorite photo app.
They're also very useful for files that aren't full of searchable text, or where that text isn't helpful in Spotlight searches. Or where you absolutely cannot move the file, like say it's an email message in a mailbox.
It also helps a lot to have a tag-friendly application for the finding of said files. Devonthink for example can use them well. I particularly like Leap, http://www.ironicsoftware.com/leap/ And for email, MailTags.
I was reading about it today, but came across lots of negative feedback about their latest update. But something like this would definitely be the closest thing. I don't really care for the sidebar itself, and I see some of these apps have their own shortcut managers/systems, like Leap (but it looks so clunky).. but yea this type of software could work out.
What's your take on Pathfinder?
Ah yeah sorry I meant to do that: say I have a bunch of videochat apps and a bunch of textchat apps and some of those apps have both videochat and textchat capabilities. I want to be able to find those apps with both functionalities. I could put them in a separate "video+text" category all their own, but then I wouldn't be able to find them when I'm looking for videochat apps - at least, not with any of the programs I've found so far.
That example seems trivial and it is; I want to be able to layer that functionality to make it useful for sifting through 300+ apps. I was able to do this on my Mac using an application called Leap for over 2,000 apps and it's come in immensely useful. (I used to be a software reviewer.)
I've been a big fan of Pycharm since v1 (after pydev and the whole Aptana fiasco). As much as I appreciate Jetbrains throwing in the kitchen sink, I still like specialized tools for specific things, which is what OP asked for.
For example, while debugging in Pycharm you can run a quick PAW session to verify what data the API returns, hop over to Coda and tweak a CSS style and edit a template, jump over to Mou and update a doc, use Navicat to zap a record or tweak a DB setting, and then go right back to debugging in Pycharm.
Having separate tools is also especially handy in this era of MQTT, websockets, and await/async.
But to each their own.
As for Leap: http://www.ironicsoftware.com/leap/
If you have a ton of media to wade through and can't remember what went where, it's prettty handy.
Also, forgot to mention Jetbrains webstorm. Pretty handy for debugging Javascript on the front-end while debugging the back-end in Pycharm.