Good Morning.

can i model this kind of elbow support as a +Y restraint?

Thank you very much.

Of course you can. That's what it is.

Is it bolted down? Then it may serve as a Y restraint. If it will always carry a -Y load then it doesn't matter if you enter it as +Y or Y.
And what about X & Z restraints if it is bolted?
Another question - where are you locating these restraints? On an elbow node or at the base of the short vertical leg?
And what of the modified flexibility of the elbow?
You can make this as simple or as complicated as you wish. I would recommend the simplest model that produces confidence in the results. Use your output to verify the input.

Oops, I didn't see the lower diagram, thought it was resting and on teflon. Dave is right.