Thank you. I'm not a programmer. My output pane would be in Autohotkey, in order to avoid that the commandline search opens a new instance of FL with every such search - a switch (something like "-in" for "new instance: no") for it using the current instance (or just creating a new one if there is no existant one) had been asked for here in 2013, but without such a switch having been introduced in-between.
Since it should be simple to internally (i.e. in FL) redirect the variable content to the clipboard instead of writing the variable content to a file in the file system, in fact even easier, I had hoped there might be a solution available to a non-programmer.
So I'll install a 1gb RAM disk, then with the -o switch write into a file on that, then from Autohotkey check for any change of that file, then read that file into clipboard, I would have preferred a simpler solution.
A macro from the outside upon the current FL instance would also be possible, but since many options are hidden behind additional tabs (which cannot be accessed by short keys but just by mouse clicks if I'm not mistaken), this would be very cumbersome and lenghty in execution time, albeit possible.
Switches for not creating another instance, and for directing the output to clipboard, would both be more than welcome.