Text replacement no available or working on Mac messages

I've seen other threads about this and no one seems to have a satisfactory answer. I can use text replacement on all apple devices except for my Mac with Messages. I can pull down the menu, go to system settings, show the text replacements, and then copy and paste what I want, although it's laborious each time.

Today I realized I don't even have "Text Replacement" available in the Substitutions drop down menu!

Those are my choices. If I select "Show Substitutions" I get this menu:

and when I click on Text settings it opens the System Settings and I can find all my text replacement entries, although none of them work in messages. Clicking on the Menu Bar of the floating window that appears with the above image, I get this:

Seems like we are getting somewhere, right? Not really. If I leave that floating window open, then my text replacements will work, but only if I have that window open. Seems like a real difficult way to use a feature that is supposed to make something Simple. Can someone please fix this issue?