I am new to English and this forum as well. You may have sensed it already.
Here is my question:
Can plural noun be followed by another plural noun?
As in the example:
Notifications settings
Is it correct phrase?
As to the general question you ask, yes, plural nouns can be followed immediately by another plural noun. Here is an example: "I gave each of my cousins presents."
However, your example "notifications settings" suggests you are really interested only in compound nouns, since that's what "notification setting" is. The main stress in this example is on "notification", which suggests it is a compound, since compound nouns typically have stress on the first part of the compound.
Pluralizing the first part of a compound sounds odd in current English, ?"notifications setting", though there are some archaic forms like this, e.g., "sergeants major". But in the last, the "-s" applies logically to the entire form "sergeant major".
I think your example "notifications settings" is marginal, not because of the two plural inflections, but because it is the first part of the compound that has an -s.