Add a split button widget

[Brow71189]

This would be useful to have a button that does a default action, but the user can select related, but less frequently needed options by clicking on the right part of the button which acts as a drop-down menu.
Here is an example of such a button:
https://www.w3schools.com/howto/howto_css_button_split.asp
Although it would be nicer if you actually have to click on the dropdown part in order to open it.