Here is an OSMC add-on that will launch RetroPie in my Dual-Boot RetroPie / OSMC build:
OSMC RetroPie Add-On (Dual-Boot) (5972 downloads)
The purpose of this add-on is to allow the use of any skin within OSMC (even those that don’t support custom script shortcuts), so you don’t lose the ‘Launch RetroPie’ button if you make any changes etc.
Another benefit is that the whole partition switching process is now contained in its entirety within this add-on, so no more random /ss/ or /noobs/ folders lying around! I will be using this add-on in all my future builds and have also uploaded it at the following location so you can load it in as you would a regular KODI addon:
(there are folders inside the above link for OpenELEC / OSMC, and then DualBoot / Triple Boot. Choose the path for your build and you will get to the .zip file you need to install)
*Please note this particular add-on will ONLY work in OSMC! I have other add-ons specifically for OpenELEC so if that is the OS you are using then please use those as this one will not work in OpenELEC.
All the best.