There's no way to change the Time Signature on one measure...However. If you put the time signature to 1/4 you can pretty much do what ever time signature and you can change it in one measure
Something I like to do is to make my own metronome. I make a really basic sound with the pulverisateur (or any synth) and manually place the number of notes in the time signature down in a region, name the region as whatever time signature it is, and loop it for as long as I want. It's enabled me to do multiple time signature switches.
There's no way to change the Time Signature on one measure...However. If you put the time signature to 1/4 you can pretty much do what ever time signature and you can change it in one measure