Browser control through Synapse 3: no Ctrl-W?

A few months back I decided to invest in a proper mouse, and I haven't owned gear as fine as my Naga Trinity before. But seeing how nice it is in hack & slash, I would like the same multi-functionality in other places as well. So, I created a second profile for browsing. But there's something strange: the page up and page down key bindings are working fine, but Firefox nor Chrome is listening to Ctrl-W commands to close browser tabs, nor does it listen to things like Alt-tab to switch windows. In other applications the Ctrl-W or Alt-tab bindings don't seem to function either. Is there a way to enable this under Windows 10? Many thanks for any pointers.