Yes, of cource!
Do you use VKB configuration utility VKBdevcfg.exe? If no download it.
Launch (joystick must be connected). Open Profile - Buttons - Physical layer tab.
This is an example of simple buttons.
Check Poll and press joystick button, you want to be Shift. You will see red dot in its cell. Click this cell. Button mapping wizard dialog appears.
Select SHIFT from combobox. Press Set button on action tab. Controller will restart and after that your buntton will work as button modifier. More information you can get from user guide
https://yadi.sk/d/7FMUBTQa3Q9uH5.
Official software and firmware files you can find here
http://ftp.vkb-sim.pro.
Up-to-date betas (working, tested)):
Configurator
https://drive.google.com/drive/folders/0B1WRiD1czmcHMVBEcVQ0dndyNG8,
Firmware
https://drive.google.com/drive/folders/0B1WRiD1czmcHbklBX2hMSEN0bzA?usp=sharing.
If you will have additional questions or troubles please show screenshots of Global - Common tab and Global - external one.
Good luck!
PS
My pictures show an example. I use Mamba controller. You controller name will be another. Also your cell number (button line number) willl not be the same.