It is TouchOSC:
https://hexler.net/touchosc
The template was made using the first edition of TouchOSC, but it also works with the second edition. I personally use the second edition. The developers of TouchOSC also make the Protokol app for analyzing an OSC traffic.
Sorry, but you have no solution for what?
I am not sure to understand what you mean by that? 
Hi David,
thanks.
My problem is, that I can (for the edit: can’t, that was a mistake) send osc messages with the integrated thing of GP. Very good, very easy.
But I think I have to send three messages to change the layer of the Totalmix layer
/setSubmix
/1/businput
/1/volume1
At the moment I’m not able to do that with the script. I scripted a little bit in the past, but I think I have to learn more about that.
My solution at the moment: I set the layer fix in Totalmix, because I only have to control my personal IE Mix. The rest is not needed. But I would like to.understand and know everything about that 
Why not, exactly?
If your goal is to mix you own IEM, you don’t need to set the submix, you should rather restrict the OSC remote channel you use to the submix you need in the Total Mix OSC settings. Hence you won’t modify inadvertently other submixes like the FOH submix.
The proper OSC command is /1/busInput 1. (With capital I for Input and 1 as a value)
If you want to be able to switch between busInput, busPlayback and busOutput you could use a radio group of buttons.
And this can be adjusted by a GP slider.