Also, I started coding a "get" method for canvases, which happens to do what Miller describes in his comment about the above patch.
so in the meantime you can either apply a diff to the sources of Pd, recompile Pd and change your patch accordingly, so it is incompatible with all past versions of Pd (and probably a number of future versions of Pd as well), or use [f] to store the values of [tgl] and query them via bang, change your patch accordingly and be happy.
i'm not saying that things should be kept deliberately complicated, but it is really simple to implement what you need with what is there.
mfdst IOhannes
PS: you could also "double bang" the toggle, which wil give you the current value and will restore this value. or use "bang" + "set <value>" to restore the original.