Check this blog at the first. We've modified our problem selection process. Now you can use this form to submit ideas. If you submitted a problem on Ninja-Setters, send it again through this form, I can't access Ninja-Setters anymore.
Still, we need approximation problems (although it doesn't mean we don't need other problems), please submit them if you have any.
If you have questions, please send an email to me (firstname.lastname@example.org) or ask in the comments. Please do not message me here.
Update (May 21): Nowadays we prefer full contest proposals instead of single submissions to the Google form mentioned above. Send your full set to me through email. Specify the contest (Easy/DSA/Circuits) in the subject. If you previously sent your problems through the form above, mention it.