You could use a script to toggle between the commands. Here's a python script.
Copy the following into a file
#!/usr/bin/env python
from subprocess import Popen, PIPE
setting = Popen(['gsettings', 'get', 'org.gnome.nautilus.window-state', 'side-pane-view'], stdout=PIPE).communicate()[0].rstrip()
if setting == "'places'":
Popen(['gsettings', 'set', 'org.gnome.nautilus.window-state', 'side-pane-view', '"tree"'])
elif setting == "'tree'":
Popen(['gsettings', 'set', 'org.gnome.nautilus.window-state', 'side-pane-view', '"places"'])
Save it as ~/.pane-toggle.py
. Make it executable
chmod +x ~/.pane-toggle.py
Open the Keyboard settings and go to the Shortcuts tab. On the left, choose custom shortcuts, and make a new shortcut with the '+' button. Name it whatever you want. For the command, use
/home/username/.pane-toggle.py
.
Now just set the shortcut to what you want (press enter while it's highlighted).
Of course you can name the file whatever you want and put it wherever you want, just be consistent.