You cannot have the existence of a plot depend on an observable, so you cannot have x scatter plots where x changes dynamically. At least not how things currently work. You can always concatenate the data and work with a single plot as suggested above, not sure why you don’t want to / can’t do that.
PS: Actually you can do it but you’d have to write more complex logic that adds and deletes the plot objects, renews observable connections etc. Probably not worth it