Hello,
don't worry, as far as I know such questions are not well documented in the various manuals.
Yes, you can do it afterwards.
Very quick and hopefully complete answer
draw an open line or import it, save as i3s file, open the i3s file, resample it to your desired resolution (Edit -> Line set -> Resample), map a variable (Tool -> Map Object) like water depth, save as distance-value file., open the file and view in 1D view.
Have a look also in the BlueKenue reference manual or tutorial.
Best regards,
Clemens