If I understand correctly this time, you have 4 datasets, you want to plot one of them and you want to control the smoothing with the slider. correct?
save all your datasets in a list (cell array if the sizes are prone to change which is quite likely, or they are tables or whatever), and keep a separate property which tells you the index of current plotted dataset.
Then when you choose to plot this dataset or the other you update the currentPlottedDataSetIndex property and plot.
The slider should have a callback function which also plots argain.
when plotting you take the desired dataset from the list (using the index saved in the currentPlottedDataSetIndex property), apply smoothing then plot it.