Can't split and drag sections

I’m new with Audacity, but I’m a very experienced user of other DAWs.

Checking this video, I want to do exactly this. Make a split, and then move the right hand side portion of the sound. But when I’ve made the split using Cmd + I and switched over to the Time Shift tool, this does not work—it moves the entire audio file, almost as if there was no split. But there is.

What am I doing wrong here?

I’m using Audacity 2.3.3 on MacOS 10.14.6