Maybe someone could code an extension that allows to type a value which then inverse modifies the given timeline Event length.
For example if you have a timeline Event of 1 second length and you use the extension you would type-in a value of 0.1 which then would automatically set the new Event length to 10 seconds. Or you would type-in a value of 2 and the resulting timeline Event length then is 0.5 seconds.
Such an Extension would help a lot to correctly prepare a slow motion (or time lapse) effect.