Sharing only one window or part of a screen in Zoom

The following link from a college refers to sharing part of the screen in Zoom https://www.etsu.edu/helpdesk/documents/zoom-share-portion-of-screen.pdf

However when I click on "Share | Advanced Sharing Options" as follows:

There are no partial screen sharing options available:

So then - how can part of the screen or only one window be shared?

Update When clicking directly on the green "Share" there are no options at all for customization - not any dialog or any buttons.

There is only this:

Another update OK the issue is that I had sometime in the past set up "Automatically share desktop" in Prefences . I'll make that an answer per @grg

Solution 1:

Don’t click the arrow next to the share button — just click the green Share button itself.

‘Advanced’ doesn’t refer to the advanced options dialog, just the tab at the top of the normal window accessed by clicking Share.

Solution 2:

The issue is that I had sometime in the past set up "Automatically share desktop" in Prefences . I had forgotten about having made that selection.