What is the keyboard shortcut to switch between open applications inside Citrix?

Here is an article from Citrix support center on "Enable toggle between applications using Alt-Tab keys within a remote desktop session"

Launch Regedit.exe on the client device to edit the registry For Windows 32-bit OS, navigate to the key HKEY_LOCAL_MACHINE \SOFTWARE\Citrix\ICAClient\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard\

For Windows 64-bit OS, navigate to the key HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard\

In some cases configuring User based Setting also helps: HKEY_CURRENT_USER\SOFTWARE\Citrix\ICAClient\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Keyboard\

Set the below Value.
Value Name    TransparentKeyPassthrough 
Value Type    REG_SZ 
Value         Remote 

Note: You have to exit Receiver and launch it again for this change to take effect.

1. Close Citrix Remote Desktop, if it is already running.
2. In our local machine, go to ‘Regedit’ and open ‘TransparentKeyPassthrough’. Set the value to ‘Remote’ and close.[HKEY_LOCAL_MACHINE → SOFTWARE → Citrix → ICA Client → Engine → Lockdown Profiles → All Regions → Lockdown → Virtual Channels → Keyboard]
3. Login to the usual Citrix page. Before clicking on the ‘Remote Desktop’, check the ‘Preferences → Session Settings’. Choose ‘Fullscreen’ from dropdown.
4. Click ‘Remote Desktop’ now.
5. Login to the Remote Desktop
6. You should see a blue bar at the top.
7. If you don’t see it, press Ctrl + Alt + PAUSE. Now you should see the blue bar.
8. Try Alt + TAB, and you should be able to scroll through the open applications within remote desktop. Also, this enables you to save screenshots in the remote itself.
9. If you want to maximize the screen even more, Press Shift + F2.
10. To revert, you can press the same key combinations again.

Got it working. Just to clarify:

In the Registry Editor -

For 32-bit OS, Citrix is under HKEY_LOCAL_MACHINE\SOFTWARE\

For 64-bit OS, Citrix is under HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\

However, I just changed it under HKEY_CURRENT_USER, and it worked.

Also, I chose "On the remote computer" from the "Keyboard" dropdown in the RDP Connection Local Resources tab.