My PI 3 is currently running NOOBS on a Class 10 SD-Card.
I see multiple guides online, however I cannot find one that doesn't involve formatting the SD-Card.
I want to dual-boot another OS like Kali or Android (Emteria), aside from NOOBS.
I do non want to format the card in order to preserve the current OS instillation
How can I install another OS aside from my current one without formatting all the data and the OS installed?
Simple answer - you can't!
If you search this site you will find recommendations not to use NOOBS, and if you want multi-boot use PINN
Neither allows you to add OS after initial setup.
Long answer - (On Linux nothing is impossible) Using a Linux computer you can copy/shrink the OS partition; perform a fresh multi-boot install then restore the saved partition. There are a few adjustments to fstab, cndline.txt etc. required.
