As a prerequisite I want the notion to be clarified.
Not every tag has a tiddler with the identical name, automatically - you have to create it.
Since also not for every tiddler there is a tag with the same name, a tiddler with a name of a tag must be some kind of a special tiddler - is it?
So what is the offical naming of these kind of tiddlers? Companion tiddler?
Let's come to the initial purpose of this post. In my wiki I try to make a companion tiddler for every "normal" tag - just to be able to structure / cluster / aggregate the tags by tagging them again with some "higher meta tags". And because you can't tag other tags directly, you have to create a companion tiddler first and then tag this one. This is the solution that came to my mind - if you have other / better suggestions to strructure your tags just tell me, please.
So from time to time I forget to create a companion tiddler for a tag. Then it is kind of hard work to find the tags without companion tiddler, manually.
you can use:
<<list-links filter:"[tags[]]">> .. to show all used tags. Those, that are shown in italic don't have a corresponding tiddler.
<<list-links filter:"[untagged[]]">> to list all tiddlers, that are untagged.
You may also have a look at the right sidebar: More: Tags tab. and the TagManager which links from there.
see: http://tiddlywiki.com/#untagged%20Operator:%5B%5Buntagged%20Operator%5D%5D%20%5B%5Buntagged%20Operator%20(Examples)%5D%5D%20%5B%5Btags%20Operator%20(Examples)%5D%5D%20%5B%5Btags%20Operator%5D%5D
Take a look at Eucaly's answer
Eucaly, that's perfect so far. Thank you, man.
I know the "system" filter, but I didn't know the "missing" keyword. Are there others keywords as well? Is somewhere a list of keywords?
Ok, by trying to answer the question for a list of keywords on my own my best guess would be http://tiddlywiki.com/#is%20Operator
If the list would consist of tagpills instead of pure links then - with a click - you could see the tiddlers using each tag - and you would have more context about the meaning of the tag - what would it make easier to tag the tag itself into a certain category.