[kiwidude]

No the functionality doesn't exist in any of my plugins, the closest to it in terms of code required is the User Category plugin which has the code to view/expand a node in the tag browser.

It's not a feature of personal interest/use nor have I seen it requested so it isn't something I am rushing to add to the View Manager plugin. If someone else wants to submit a patch or indeed as BetterRed suggested incorporate into the tag browser options within calibre itself then those are your more likely options at this point.