what version are you using? 2.0 or 3.0
2.0 you can add toggle keys for each shader/effect in their respective file for example McFX.cfg open it, search RFX_ToggleKey and you will see that exact entry to apply the key, just rename it VK_blank. You can find keycodes here if needed
pastebin.com/csHY60sh
3.0 is possible as well now
, Thanks crosire!! time to go mess about haha