Why? What about using "standard copy/paste key bindings" (which are now active by default) and clicking your way through the graphical icons and the drop-down menus?

But it's probably difficult to get fancy effects without learning TeXmacs more deeply. Unfortunately I can't compare with LyX (I happen to be a TeXmacs believer... but by no means a guru -- not being "motivated" enough to study the manual!)

An important thing is to take notice of the key binding for a command when you've finally found it in the menus. Also, if you remember a LaTeX construct, try using it -- sometimes it's available under the same name, e.g. \setminus.)