Sorry yes that's psreadline not posh-git like I commented. I wouldnt' call that a drop down though, that's just adding to the output isn't it? You know I've no idea how that works, could come in handy actually I should learn.
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.
