Hey, you were right, I could adjust to just one column and one "reach".
Although the error message now says "Error: Number of observed files should be: 1" I can still not select that file. Or at least selecting it, does not make a difference.
The format of the observed file is just as the example file and as the "help" description in R-SWAT.
When I tick the "display observed data" box, it also still says Error: subscript out of bounds.
Do you have any more ideas?
Thanks!