Thank you for your reply!
I also found recovery.cmdline in the NOOBS zip file, leading me to assume it only existed pre-installation. What you're saying is that after installation of OS(es), it is put in a separate partition, and can still be accessed by opening/mounting the "RECOVERY" labeled partition.
The reason I couldn't find the file is that I am using Ubuntu on my laptop. When I insert the SD card, it mounts all the partitions
except the recovery partition. I had to manually mount this using the mount command, in my case:
My motivation for editing this file was to enter the NOOBS boot menu without pressing SHIFT, as I do not have a USB keyboard.