By pressing Shift+Chan+N (where N is 1-16), it is possible to select the sequence length for BeatStep. However, if the sequence is running, then the only possible way to do that while the sequence is running without a hiccup is to catch the first step. That's pretty troublesome. It would be nicer if the current sequence wouldn't reset to the first step. But either continue with the new length for the current sequence, or the change should take effect on the next loop.