I can't select more than 1 record in choice after applying filter

As a user(table 1) I want to select from 5 people(from table 2) so that they are connected. For the moment I manage to assign the relationships of these 5 people(to them the id is assigned in the string in table 1), and then using search/lookup assign me in table 2. The problem starts when I want to filter the choice, so that when a person in table 2 already has me, it does not show up in choice. When I add the filter I can only assign 1 person, when I select the other one, it replaces the 1.

after click

What I want to do is that the moment someone assigns a user to himself, in other users this selection option disappears.

The problem is because your filter is kicking in immediately as soon as you make a choice. When you choose a name, the filter knows that it has to remove that name from the list, so it no longer becomes a choice to choose from. For multi-select to work properly, all options need to remain visible.

I’m assuming you are making these choices directly on a detail screen, so you are updating the row in real time as you make each choice. I suggest using an Edit Screen for this, so the choices aren’t saved until you click on submit.