If you have a specific button graphic you want, let me know. I can make it. I have a Photoshop template that makes it pretty fast.
@Eclsnowman Thank you for your offer. I’ll come up with some button graphic soon. 
But first I need to know, whether I’ve got a chance to read the settings (call M501) without a WiFi connection. By now I was not able to read the actual z position. Any idea how I can grab this value?
Not sure. I have only ever used the lcd with the wifi module added (which allows a wifi to serial bridge). Perhaps you could use a usb to serial adapter in place of the lcd on the tx/rx just during the setup process, then connect the lcd once you know the offset. Or just guess and check by creating multiple versions of .gcode files which change the value, them save them with m500 in the gcode on sd.
Now I have installed the wifi modul. When I call “M501” to read the settings I got this:
Connecting…
Printer is now online.
M501
SENDING:M501
But when I call M105 I got this:
Connecting…
Printer is now online.
M105
SENDING:M105
T:23 /0 B:0 /0 T0:23 /0 T1:0 /0 @:0 B@:0
So the connection seems to be ok. But why I don’t get the listing? Is this related with the firmware I flashed? I took the the one you provided via YouMagine.
If I recall I had issues with m501 too.
@Eclsnowman Thank you for your reply.
How do you then read the actual settings?
I could manually write the z offset on a piece of paper and stick that to the printer. But you know, that’s a bit outdated. 