This functions more or less identically to using a media out value, but the
desired speed is preserved through block length changes, even if the block's
length is reduced to zero (i.e. no rounding errors).
Previous iteration used some "magic code" that added clips automatically to the
timeline. This was functional but ultimately outside of the undo commands'
control meaning nodes could be infinitely added and abandoned. This makes the
add process part of the undo command which means it's all undoable as the user
would expect.
itsmattkc