Adding two control keys and another keyboard keystroke can be done, it is tricky, but it can be done. And Yes, the Driver team is working on making it an easier task to perform.
Once you have done it once or twice, you will get the flow of being able to add the needed keystrokes quickly.
This is a Windows-only process.
Let's get to it...
The first step is to make sure that your Xencelabs devices are connected and that you have opened up the Settings program.
Once open,  select the application icon in the Application row to which you want to add the custom button settings.
In this case, I have selected the "all other" icon and  the Quick Keys.
 I'll be setting this custom code Ctrl+Shift+3 on button 1.
 I have clicked on Set A button 1 and selected Keystroke.
I have removed the previous  Shortcut Name and entered in Ctrl+Shift+3. This will be displayed on the Quick Keys OLED display for button 1.
 I then clicked in the Keystroke Keys, then clicked on the Clear field.
Now comes the tricky part.
 Drop the menu down for Special Functions.
 Click on Add Special (nothing visible will happen)
 Click in the Keystroke Keys field, and  press Crtl and Shift. You will see Ctrl + Shift placed in the field.
 Going back to the Special Functions dropdown, click on Add Special once more.
 Click in the Keystroke Keys field and enter the last Keystroke. In this case, it is 3.
 Click OK
 The Keystroke is now set up and ready to use.
Please know that the Driver team is working on making this a more straightforward process.