Automatic message by nightbot

I don't think that is currently possible with Nightbot, you need to use other bots such as streamelements

Right @Plaid Raccoon! But how do I do that? Do you know the command? If you can help me with that!
NOTE: I also use streamelments.
Thank you.

Hey @Wooden Dragon!

This is the NightDev's forum, we won't provide help regarding products that are not made by NightDev, sorry about that, but I hope you understand why.
For help regarding Streamelements products, join their Discord.

@Polar Cat I really want from NightDev, because I see the nightbot responding in this way in several streams.

Are you sure it's Nightbot and not Streamelements' bot?
The only way I would see that possible in by using their API, I quickly had a look at their dashboard and I failed to find such API link to have in-chat notifications outside of their own bot.
As I said before, we can't help on Streamelements products because 1. they're competitors and 2. we do not know their products, sorry.
So once again I'm going to advise you to contact them on their Discord server. Ask them for their in-chat notifications API or something, even though I don't think it's open to the public.