Hi Larusur,
We appreciate you reaching out through Apple Support Communities about this issue creating playlists on your Mac to transfer to iPhone. We're glad to look into it with you and help in any way we can.
Please let us know more about what's going on. What happens when you attempt to create a new playlist in the way you're used to? Are you syncing your music to iPhone while it's connected with a USB cable?
Other than updating iTunes on your Mac, have you had any other recent changes, such as updating the software on your iPhone, or changing to a new iPhone?
So that we're on the same page, please let us know the following details:
- Your model of Mac (Check under Apple menu () > About this Mac)
- The version of macOS installed
- Model of iPhone (Check under Settings > General > About)
- Version of iOS installed
We'd also like to share the following guide with detailed information to help with syncing your iPhone with iTunes on your Mac:
Use iTunes to sync your iPhone, iPad, or iPod with your computer
Let us know if it helps, or if you've got any questions.
Have a great day!