I was going to suggest binding a sequence of toolbar-toggle LFUNs (at least two, one for the table toolbar and one for the math toolbar) to a key, but it turns out that may not work. The documentation for toolbar-toggle says that it rotates through on/off/auto, but when I tried it, it rotated through on and auto (never off). That seems to be consistent with the View > Toolbars menu no longer toggling a menu completely off if it has the auto option (http://article.gmane.org/gmane.editors.lyx.general/61201/match=toolbar+off).
So the only thing I can suggest is to create a new UI file where the toolbars do not have the auto feature, and use that when you want to go fullscreen. Paul
