You can add tags to your reminders to keep them organized, then use the tag browser to find tagged reminders across your lists. Tags are available for reminders that you’ve created in your iCloud account.

To learn more about this topic, visit the following articles:
Organize reminders on your iPhone, iPad, and iPod touch: https://apple.co/3KoYVwq
Use reminders on your iPhone, iPad, and iPod touch: https://apple.co/3Kr8V8c
Reminders User Guide for Mac: https://apple.co/3hO14FA

Additional Resources:

GetSupport for iPhone: http://apple.co/iPhone

To subscribe to this channel: https://www.youtube.com/c/AppleSupport

To download the Apple Support app: http://apple.co/2hFtzIv

Apple Support on Twitter: https://twitter.com/AppleSupport

For more videos, go to Youtube Apple Channel