you're amazing me again...
i can't test your code right now, but actually i'm not sure, if i have found the right words to express exactly what i want to achieve:
let me try it in other words:
i want to temporarily modify the behaviour of the (four) navigation thumbs (image_template) in that way, that, if enabled, thumbnail navigation in only one specific category is available. a "back" button or a "view all" button should disable this functionality.
just to be able to browse through one category via the thumbnail navigation of the main page, not to have to go to the archive page again and again.