Hey Jantje
I've been trying to install your 4.1 product and have fallen on this issue when trying to upload a sketch to my boards.
Program "C:\sloeber\arduinoPlugin\packages\tools\arm\bin\arm-none-eabi-g++" not found in PATH
Program "C:\sloeber\arduinoPlugin\packages\tools\arm\bin\arm-none-eabi-gcc" not found in PATH
I checked the program files and they don't exist
I had the same problem when I tried using your plugin.
Here are my details
System: 64bit Windows 10
Boards: Arduino UnoR3 (sparkfun)
Teensy3.2
I had the same problem with both boards.
As well as this, the IDE seems to not recognise arduino fuctions like digitalWrite, digitalRead, pinMode, or delay.