For the hidden VS enable/disable clickspot, you'd need to set 'L:AUTOPILOT_vs' to a value of 1.
For VS increase/up clickspot, you'd need to set 'L:AUTOPILOT_vs_up' to a value of 1, and for VS decrease/down, you'd need to set 'L:AUTOPILOT_vs_dn' to a value of 1.
In all three cases our systems code would reset those back to a value of 0, ready for the next trigger.
If you would like to directly control the vertical speed, you should be able to use the MSFS 'AP_ALT_VAR_DEC' and 'AP_ALT_VAR_INC' key events. You should be able to toggle VS hold mode using 'AP_PANEL_VS_ON' and 'AP_PANEL_VS_OFF'.