MacOS High Sierra: how can I merge 2 partitions into one?
Use the commands given below to preform the merge.


  Note: These commands will delete the noname volume, therefore you may want to backup this volume.


diskutil apfs deleteContainer disk0s3
diskutil eraseVolume free n disk0s3
diskutil apfs resizeContainer disk0s2 0


If a command fails, try prepending a sudo.