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
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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