Thank you, - and OK, the instructions are pretty short. To connect red inputs to green(or black) outputs simply drag from the input to the output. You get a wire (lead) as a straight line. Intentionally it is not possible to connect two outputs. Add pads later (right click on the wire). Try the letter L to get a working sample, an adder for two two-bit-numbers. I will think about the palette, actually I was proutd it worked and left more space for the circuit. What I am missing most, is a way to mark and drag (or even copy and paste) more than one gate.

@ polle: Thank you, this was very helpful, because I just found out that the checkbox "Lock scenario" only exists in the English version of Greenfoot. Freddy apparently has set the language to German (in the configuration file bluej.defs). @ freddy: Stelle zum Exportieren die Sprache in \Greenfoot\lib\bluej.defs auf english, dann kannst du den Geschwindigkeitsregler in das Applet übernehmen.