macOS – How to Enable 3-Finger Drag in macOS Catalina?

I believe I figured out the difference:

Dragging:

1. Double tap and hold to begin dragging.
2. Release the mouse.
3. Depending on the amount of time that has passed, moving the mouse will do one of the following:
   • Brief delay: moving the mouse continues the dragging, essentially behaving the exact same way as drag lock. The cycle is then repeated once you release your finger.
   • Longer delay: dragging is stopped.

Dragging & Drag Lock:

1. Double tap and hold to begin dragging.
2. Release the mouse.
3. Moving the mouse will continue dragging.
4. Tap once to stop the dragging.

It's that brief delay that was throwing me off. There doesn't seem to be any way to customize the length of this delay. One thing that does help, though, is figuring out exactly how long this delay is. One method for figuring this out is the following:

1. Drag an icon from the dock a tiny bit so that if you were to release it, it wouldn't be deleted.
2. Release the mouse.
3. Observe how long it takes for the icon to move back to its place. That is the exact amount of minimum time that you should wait when you are finished dragging something.

Some older Macs only support two finger scrolling on the trackpad, not three. Since you're not seeing a setting for three finger drag, I'd guess your hardware just doesn't support it.

Are you able to do other gestures that require more than two fingers? If not, it's probably a hardware limitation, and you could just get a Magic Trackpad.