it seems like almost a bug, that in M650 I cannot configure side button for 'keyboard shortcut' (in gestures) so that the side button emulates Ctrl key pressed/released as the side button is kept pressed/released.

I would like to press side button and use mouse wheel to zoom in/out in browser, but this is now not possible in Options+.

The side button should emulate Ctrl key when the mouse doesn't move, but when mouse moves the side button should support 'gestures' instead.

I tried to fill out the "keyboard shortcut" as "Ctrl" but it doesn't work at all for "Ctrl" or "Shift" modifiers alone. Maybe the "keyboard shortcut" emulates one time press of the key combination well, but I need holding the Ctrl modifier pressed as long as the side button is hold pressed. One-time press is almost useless for modifiers.