Where does a volume controller enable in the key editor?

[ghostman]

Hi, guys! I’m sorry for my stupid question… But where does a volume controller enable in the key editor? Unfortunately, I even don’t know how is it called correct, so I attached a picture to show it.

P.S. On the picture the green block (that I drawn) was drawn for each event. I want to return this option now.

[jaslan]

Click the “+” in the bottom left to open a controller lane. Select the volume if it doesn’t open volume by default.

[Grim]

As Jaslan says the + sign will open the lane.
Judging by your description, I think you want to select “Velocity” rather than “Volume” though…this is how it would have been set at default.