@Dalmatino16 with the help of the Counter Generation you could give the lines numbers.
Then you could use the Rule engine to save the number of the line if a certain condition is met and store the line in a separate column (var_start, var_end). Then only keep those columns and use a math node to calculate the start and length. Then convert that into Flow Variables that you can then use to steer your File import.
A somewhat similar example:
You mabye could upload 3 or 4 examples with varying table starts that would represent your task. Then someone might have a look.