I use a G600. Mouse numpad is assigned for 1234567890+- and with 3rd mouse button pressed assigned for ctrl+ F1-F12
Hotbar1: 1234567890+-
Hotbar2: Alt+ 1234567890+-
Hotbar3: Shift+ 1234567890+-

I press Alt and Shift on the keyboard, rest on mouse pad. Easy access to 4 hotbars under one finger.