You can always look up the the commands in the Command helper, and view the more detailed documentation of each command. (Either push F1 when the cursor is clicked on a command, or lookup that command in the Helper. Help > Command Helper.) Here is the info about setpickingdrawfocus. (Unfortunately I've never used it, so maybe someone here will have a better application example than me. There is a small bit of example code at the bottom of the documentation.)
Parameters
(obj theview, obj focus, num what[, obj secondaryfocus, num flags])
Description
For developer use. Sets the draw code following this call to be picked as the focus when clicking or dragging. Usually you would use this to draw custom sizers and grippers on your object, and then implement an OnDrag or an OnClick event on the object that would call getpickingdrawfocus() to figure out what part was clicked.
flags is a bitwise combination of one "DETECT_DRAG" setting, as well as optional "override" bits. The override bits aren't used to define picking focus, but will cause FlexSim to override its normal drawing of sizers and bounding boxes.
DETECT_DRAG_X, DETECT_DRAG_Y, DETECT_DRAG_Z - will only detect dragging along the given axis, relative to the object being drawn. Use this with the draginfo() command in your OnDrag event to determine where the object is being dragged.
DETECT_DRAG_XY, DETECT_DRAG_YZ, DETECT_DRAG_XZ - will only detect dragging along the given plane. Again you would use this with the draginfo() command in the OnDrag event.OVERRIDE_DRAW_SIZER_X, OVERRIDE_DRAW_SIZER_Y, OVERRIDE_DRAW_SIZER_Z, OVERRIDE_DRAW_SIZER_X_NEG, OVERRIDE_DRAW_SIZER_Y_NEG, OVERRIDE_DRAW_SIZER_Z_NEG, OVERRIDE_DRAW_SIZER_ALL - these flags will cause the engine to not draw the flagged sizers
OVERRIDE_DRAW_YELLOW_BOX - causes FlexSim to not draw the yellow box around the object when selected
OVERRIDE_DRAW_GREEN_BOX - causes FlexSim to not draw the green "statistics-active" box around the object
OVERRIDE_DRAW_REDBOX - causes FlexSim to not draw the red selection box around the object when selected
OVERRIDE_DRAW_HOVERBOX - causes FlexSim to not draw the yellow hover box around the object when hovering over it
OVERRIDE_DRAW_ALL - causes FlexSim to not draw any sizers or boxes around the object
Example
setpickingdrawfocus(view, current, 20, drawsurrogate(current).first.subnodes[3], DETECT_DRAG_Y);