Reminders tags on Mac don't appear but on iPhone they do.

Hi ijustwantataco,

Thanks for contacting Apple Support Communities!

We understand that you don't see tags in Reminders in macOS Catalina.

Tags in Reminders were introduced in macOS Monterey so you would need to install macOS Monterey or macOS Ventura in order to access tags in Reminders on your Mac. You can learn more about this feature here: Tag reminders on Mac

"Add tags to reminders

In the Reminders app  on your Mac, do any of the following:

• When adding a new reminder, click the Tag button #, then choose an existing tag or click New Tag to create and apply a new tag.
• Add a tag to the title of a reminder (type the # sign at the start of the tag).
• Click the title of a reminder, click the Tag button #, then choose an existing tag or click New Tag to create and apply a new tag.
• Place the pointer over a reminder, click the Info button , click the Add Tags field, then choose an existing tag or type a new tag.
• In the sidebar, scroll to the Tags section, select a reminder, then drag it to a tag.

When you add tags, suggestions are shown as you type. The suggestions include tags you use in the Notes app. The tags you use for your reminders are also shown as suggestions in the Notes app."

We hope this helps.

Cheers!