A few years ago, there was a request to use a zero-to-three “Degrees of Separation” filter for this purpose of winnowing the Object Selector … rather than the more narrow-minded “Generations” approach. (@Mattkmmr created an add-on filter rules for Degrees of Separation from a “specific person” and the “Home Person” that could be used for reference. See FilterRules addon source)
It seems that when using the ‘Add Existing’, the objects we will most likely want are already linked to people within a couple degrees of separation of the Active Person. As an example, as I Add a sibling, most of the desired Places/Sources/Citations that already exist will already be Referenced by the people VERY closely related to the person being Added. (A similar function for the People view would have to be based on Home Person instead of Active Person or the view would be in constant upda…