I recently started using WebStorm, and I can't seem to find this feature there at all. It's the one where you pick multiple matching bits of text one by one in a file and edit them all together.
Cmd + D just duplicates the selected text.
In order to select the next occurrence in JetBrains IDEs, you can use Alt + J (or Ctrl + G on MacOS).
To unselect it, add Shift.
If you want to select all occurrences, press Ctrl + Shift + Alt + J (or Ctrl + Cmd + G on MacOS).