A folder track in the Tracks area is represented by a channel strip in the Mixer.
Note: Make sure that View > Folder Tracks is chosen from the Mixer menu bar.
In Logic Pro, do one of the following:
Double-click the folder track in the Mixer.
Double-click the folder region in the Tracks area.
Select the folder, then use the Go Into Folder or Region key command.
The Mixer now displays only those channel strips that are in the folder track.
In Logic Pro, do one of the following:
Click the Display Level button 
at the left side of the Mixer or Tracks area.
Double-click the Tracks area background.
Use the Go Out of Folder or Region key command.
The Mixer now displays all channel strips, including the folder channel strip.