here is example of modified v4.99 vcp. using lower right for any use you want. (or any space on the vcp for that matter), with simple human readable text file (xml) edits
<button row="1" column="1">spindle_plus</button>
<button row="1" column="2">spindle_auto_man</button>
<button row="1" column="3">spin_warm</button>
<button row="2" column="4">set_z0</button>
<button row="2" column="5">auto_z_plate</button>
<button row="6" column="1">rapid_over</button>
<button row="2" column="1">spindle_100</button>
<button row="2" column="2">spindle_cw</button>
<button row="2" column="3">set_xy0</button>
<button row="2" column="6">park</button>
<button row="3" column="1">spindle_minus</button>
<button row="3" column="2">spindle_ccw</button>
<button row="3" column="3">laser_set_xy</button>
<button row="3" column="4">m55</button>
<button row="3" column="5">goto_xy0</button>
<button row="3" column="6">limit_switch_defeat</button>
<button row="4" column="1">spindle_cancel</button>
<button row="4" column="2">spindle_start</button>
<button row="4" column="3">popup_pins</button>
<button row="4" column="4">goto_machine_xy0</button>
<button row="4" column="5">m58</button>
<button row="4" column="6">reset_home</button>
<button row="5" column="2">coolant_auto_man</button>
<button row="5" column="3">dust_collector</button>
<button row="5" column="4">hold_down_vac</button>
<button row="5" column="5">air_blow</button>
<button row="5" column="6">work_light</button>
<button row="6" column="2">incr_cont</button>
<button row="6" column="3">x1</button>
<button row="6" column="4">x10</button>
<button row="6" column="5">x100</button>
<button row="6" column="6">mpg</button>
<button row="7" column="2">4th_positive</button>
<button row="7" column="4">y_positive</button>
<button row="7" column="6">z_positive</button>
<button row="8" column="3">x_negative</button>
<button row="7" column="3">x_negative_y_positive</button>
<button row="7" column="5">x_positive_y_positive</button>
<button row="9" column="3">x_negative_y_negative</button>
<button row="9" column="5">x_positive_y_negative</button>
<button row="8" column="4">tortoise_hare</button>
<button row="8" column="5">x_positive</button>
<button row="9" column="2">4th_negative</button>
<button row="9" column="4">y_negative</button>
<button row="9" column="6">z_negative</button>
<button row="14" column="4">cycle_cancel</button>
<button row="10" column="3">single_block</button>
<button row="10" column="4">tool_check</button>
<button row="10" column="5">feed_hold</button>
<button row="14" column="6">cycle_start</button>
<button row="12" column="1" column_span="3" row_span="3">reset</button>
<button row="12" column="4">feedrate_negative</button>
<button row="12" column="5">feedrate_100</button>
<button row="12" column="6">feedrate_positive</button>
<button row="13" column="4">25_percent</button>
<button row="13" column="5">50_percent</button>
<button row="13" column="6">75_percent</button>