application menu with left mouse click?

[Juha Heinanen]

After using Openbox for a few years, I decided to give Xfce a try.

I'm customed to get application menu by clicking left mouse button on
the workspace.  Xfce defaults to right mouse button.  How to change that
default to left mouse button?

I don't want to change any other mouse behavior, i.e., don't want to
select Left-handed Buttons in Mouse and Touchpad settings.

-- Juha