Before asking the question, i will provide some context, as the question itself is very easy.
There are some users who register and compile forms (For the sake of semplicity, i will call them 1, 2, 3 ,4) and then 2 users who can see what they compile on the front end via views (We will call them "see1" and "see2").
"see1", can only see in his view what 1 and 2 have compiled, while "see2" can only see what 3 and 4 have compiled. (this is done via the entry filters in views, or user Id is equal to 3 ecc)

The question and need is, when another user is registering, how do i add assign him to the see1 or see2? i just need to know how to do the following:
Example: user 6 is registered and i want see2 to see his entries, the view of see2 should be updated as such (Attachments).
I just need to know how to add another filter like "OR User ID is equal to 6" in the view without manually modifying it in the back-end.
Thanks a lot