@Jack To make things easier, I have made this: msleziak.com/various/bookmarklets.html You can now simply drag the bookmarklet to your bookmark bar in Chrome.
It should work in the way I described - if I selected some part of some post (some math formula), clicking on the bookmarklet opens the new tab with the search for this specific formula.
If you decide to try it, let me know whether the bookmaklet works for you.
Of course, there is not that much difference between copying and pasting the formula into raw query. (After all, many times even after this I do edit raw query to make changes to formula or add more keywords.)
Perhaps with using the bookmarkled you save one or two keystrokers.