I am not that much of a Dolibarr developer. I’ve done a few minor alterations and do have some accepted Pull Requests, but that is mostly about the API which I use a lot. But I still want to try to give an answer.
I do not think that default Dolibarr can do what you want. I think you either need a module or you need some code inside main Dolibarr.
As I understand the Dolibarr data model, Users, thirdparties, proposals, orders, invoices, … are separate objects that are stored in individual database tables. These are linked together using fk_ - foreign key columns. So for a proposal there is a key that points to the thirdparty, and there is a key that points to the user who actually created the proposal.
Here’s some heavily edited extracted json from the api with an proposal
{
"id": "1616",
"contacts_ids": [
"488",
"488",
"2175",
"488"
],
"user_validation_id": "3",
"socid": "100",
"user_author_id": "3",
}
(The socid is the thirdparty id.)
I THINK it would be technically possible to code that Dolibarr could have an option and possible a new permission where the current user_id would have to be the user_author_id of a proposal for Dolibarr to show the proposal.
But this would have to be done both at the proposal details and at lists of proposals, and in search + possible other places.
I’ve attached pictures of my users permission in Dolibarr. I do not thinkt hat Dolibarr currently have a permissions that is needed to do what you want to do. I think you need to either code it yourself or hire a coder to make it for you.