What you want is a DATALOG file:
When you save a file, use the BUNDLE function to bundle your machine number, test circuit, whatever (include a few spare fields), plus your graph data. Get the graph data from the source, or use a local variable of the graph itself.
Wire the bundle output to the DATALOG TYPE of a NEW FILE function. (I presume you'll use a FILE DIALOG set to SAVE FILE to choose a file path).
Write the same bundle output to the DATA input of a WRITE FILE function.
Use a CLOSE FILE function to (ahem) close the file.
When you want to read a file, use a FILE DIALOG set to EXISTING FILE (or some other means) to specify what file to read. Wire the same cluster type to the DATALOG TYPE of the FILE DIALOG, so that it will only
offer files of the correct type.
When you have a file path chosen, wire the bundle to the DATALOG TYPE input of a FILE OPEN operation.
Use a FILE READ to read a single cluster - the output of FILE READ will be a cluster of the right type.
Use a CLOSE FILE function to....
Out of the FILE READ function, you can UNBUNDLE BY NAME the data and send to the graph and the other fields, or, if you're clever, you can use a cluster on the screen, and not unbundle it. That's harder though, since you probably want the text fields to be controls (inputs) and the graph to be an indicator (output).
Hope that helps.