Better pattern for relate domain
The pattern used by #2474 (closed) could indeed be improved when there is only one id selected. In this case it will often be better to use an '=' instead of 'in' like that the domain inversion of the client can force the value.
We don't want to make clause like (field, 'in', [1]) behaves like if it was an '=' because we want to let the choice of the behaviour (force value and hide column) to the developer.
So I propose to use this pattern when it is possible:
If(Eval('active_ids', []) == [Eval('active_id')], (…, '=', Eval('active_id')), (…, 'in', Eval('active_ids')))
I think it will require first to have #5221 (closed)