Ah! I wasn’t aware of that trigger. However, doesn’t that put the palette up as soon as the title matches? I might not want that. And title might not be the key. (URL is obtainable via Cmd+L, Cmd+C in Firefox.)
Would switching from Firefox to Safari help? (I might but right now HTML5 Canvas behaviour is better for me in Firefox.)
You can always set the palette to a hotkey if you want to choose when it's displayed. As for browsers, this method should work just as well with Firefox as Safari or Chrome, but if you'd rather define macros by URL than title, I would recommend one of the latter, as you can then just use the %FrontBrowserURL% token to acquire the URL programmatically, which is much faster and more robust than going through the clipboard. For the URL method, you could do something like this: