Is there a tag for math-challenges ? challenges? Something like that?

Would creating one be against community guidelines?

@Nick You can look on meta at the discussions tagged on-site-contests to see what other users think about this.

@user170039 Proposal was declined.

@MartinSleziak thank you

I will mention that there is also tagging chatroom. (But the question whether there is suitable tags is probably less important for you than the question whether this type of posts is allowed.)

Hence the proposal to spin-off a community for this specific content.

Challenges could be disruptive to MSE as it functions now.

Well, as you can see from meta, such questions have been posted occasionally.

Perhaps you can compere whether your intended question is similar to the ones in the past. And, of course, if you plan to post many of them that changes things a bit.

Here is the post on meta related to that proposal: Area 51 Proposal: Mathematical Challenges.

BTW there exists also a chatroom (on this site) called Mathematical Programming Challenges.

@MartinSleziak that's great!