It's as close to a dropdown as you can get in the CLI without putting GUI elements over the top. Try

    gci -  then ctrl+space

The available parameters appear on the screen, you can select one with the arrow keys, and tab, when you choose one and press space, they all disappear again. It's interactive, dynamic, it changes depending on how much of the parameter name you've typed - it's not just printing to the screen and stuck there.