@OP
I asked right the same thing some two weeks ago, in both the English and Japanese forums, and I am pretty sure that possibility does not exist (yet).
And guess what: I got exactly the same stupid-dumb answers like "why don't you drag it to the hotbar".
After I explicitly explained I, just like you, wanted to use the item in a macro.
...
You're actually quite lucky you didn't get the "Why do you want to use it in a macro? What is a macro?" one yet.