Catalina changes how content on iOS devices are managed. Where in earlier versions of macOS the iTunes app was used, in Catalina the Finder is now used manage content on devices. See this Apple support article for general information: Use the Finder to sync your iPhone, iPad, or iPod with your computer.
How to Copy Tones to Your Device
- Open a Finder window and connect your device to your computer using a USB cable.
- Your device appears in the sidebar of the Finder window. Click the device to select it.
- If prompted, trust your device.
- Drag your tone file to the finder window content or your device listed in the sidebar. You should see a green "+" icon next to your cursor.
- Release the mouse button.
- The Finder should show you a message saying it is copying the file.
- There is no tab for managing tones on the device view in the Finder. This makes this feature hard to discover.
- You can also copy and paste a tone file into the device window in the Finder.
Finding your ringtones made with Ringer
Ringer for Mac stores the ringtones it creates in a folder under its control as required by Apple for secure apps. You can show this folder in the Finder by choosing the 'Show Ringtones in Finder' item in the Ringer File menu.