Group questions are discouraged across the whole Stack Exchange network.
This is a Q&A site, and for there to be Answers, there have to be Questions.
However, questions that don't have just one answer, don't work, there are a number of reasons, but primarily, it means there is no one right answer.
Typically, different people will know about and answer different things across the network, and if they only know the answer to one part of the question, one of two things happens.
They don't answer at all. This means the whole site has lost out on knowledge, and puts the site at a disadvantage for people from Google.
They answer the half question. This is better than 1. but still not idea. It means it probably can't be accepted and it looks "unsolved" forever.
Note that there is a line. Someone might have 2 closely related questions, for example they are trying to do one thing (e.g. can't delete a file) and there are two issues stopping them, (e.g. Can't select a file and can't find trash). Use your judgement for that.
So what do we do?
First, comment. Ask the person to split it up and see if they comply. Give them a couple of days.
Then close it. It would be nice to edit it yourself to remove one of them, but that will annoy them even more. And you can't repost their question, because you (the OP) can't answer the questions asked of them.
Closing is the right option. Too broad covers this - there is no need for a custom close message.