Originally Posted by Innomen
I'd like to be able to double click the tags field and have the tags box expand or otherwise give me instant access to the tags of the book in question but all it does is launch the document for viewing.
If I am reading this correctly, you want to directly edit the tags on the library spreadsheet. You are also wondering if the tag editor (not the same as the tag browser or manage tags) is available outside the metadata editor.
For the first, on windows you click in the tags field and press F2. This opens the cell on the spreadsheet and makes it editable. You can also control what double-clicking on a cell does by changing the tweak "Control behavior of the book list (ID: doubleclick_on_library_view)". For example, you can make double-click open the cell instead of launching the metadata editor.
For the second, there isn't any way to get to that tag editor except in metadata edit.
Quickview will help navigate the tags for a book, which might help depending on what you are trying to do. For example, Quickview makes it very easy to explore which other books share a tag (or series or author or many other things) with the current book. You can Quickview the tags of a book by single-clicking in the tags cell for that book then pressing Q.