How about tagging a collaborator account for instagram reels and posts?

No, this we have not built in so far, as we try keep it as sleek as possible and deliberately not build in all the native functionalities (though in some cases, of course, we might review that and adapt). Overall, if you catch the right name + “@” it will activate it once online. We would still recommend to check and set up tags natively (i.e. directly in the social media platform you are using).