I want to make a horror game, and in the instructions or notes ill put “viewer discretion is advised”. is this tolerated or not? just wanna know.

No.
But this belongs in Questions about Scratch. I'll ask so it can be moved there.

Even if you do place a ‘viewer discretion’ warning, it will probably be taken down since Scratch is for ages 8 to 16.
So I would say, either keep the project unshared, save it to your computer, or delete it to comply with Scratch's Community Guidelines: https://scratch.mit.edu/community_guidelines/

if you plan on making a horror game, please make it suitable for all ages.

Sadly, probably not a great idea to make a horror game if you don't think it is suitable for an 8 year old, as that is the lowest recommended age for Scratch.

--kitti-kat-- wrote:

Sadly, probably not a great idea to make a horror game if you don't think it is suitable for an 8 year old, as that is the lowest recommended age for Scratch.

Correction: 0 years old, not 8.

historical_supa wrote:

—kitti-kat— wrote:

Sadly, probably not a great idea to make a horror game if you don't think it is suitable for an 8 year old, as that is the lowest recommended age for Scratch.

Correction: 0 years old, not 8.

Judging by the fact that coding in scratch usually requires you to be able to read, I don't think zero-year-olds would be able to use scratch. Nor do I think the developers think that.

historical_supa wrote:

--kitti-kat-- wrote:

Sadly, probably not a great idea to make a horror game if you don't think it is suitable for an 8 year old, as that is the lowest recommended age for Scratch.

Correction: 0 years old, not 8.

[off-topic, don't be mad at me for being off-topic]Goodness gracious, what kind of person would let a 7-month old use Scratch?[/off-topic, don't be mad at me for being off-topic]

historical_supa wrote:

--kitti-kat-- wrote:

Sadly, probably not a great idea to make a horror game if you don't think it is suitable for an 8 year old, as that is the lowest recommended age for Scratch.

Correction: 0 years old, not 8.

Well, I said recommended age, which is 8-16. Younger ages are allowed here, but Scratch is based more around ages 8 and up.

I'm not sure quibbling over the exact age requirements here is constructive. Regardless, everything on Scratch should be appropriate for all ages. Putting content warnings or age restrictions on projects doesn't change that, sorry.