Category sharing is a Doneit Premium feature, please make sure that you have purchased the Doneit Premium first, you will then have multiple ways to share a category with another iCloud user that you can find below: 1. By swiping on the category row from left to right and tapping on the 'Share' button on iOS and iPadOS. 2. By long-pressing on the category row on iOS and iPadOS or by right-clicking on it in the sidebar on macOS and then selecting the 'Share' option from the menu. 3. By tapping on the 'Settings' button in the top right corner of any category’s tasks list and then tapping on the 'Share' button on iOS.