Hi everyone,
I'd like to be able to set up an action on a filter that will filter another layer based on a common attribute. More specifically: I have a layer which contains road traffic accidents with a unique ID (id_accident). I have 2 other layers (casualties and vehicles) which relate back to the accidents layer with a matching id_accident field. If I filter the accidents layer on severity, I'd like this to then filter out any features from the other 2 layers which don't have a matching id_accident value. Basically, exactly what is possible as a layer selection via the map widget (seen in the below screenshot), but on a selector widget instead. Does anyone know if this is possible?

I do have relates set up between the accidents and casualties/vehicles layers, but I'd like to be able to set up filters based on the fields in the casualties and vehicles layer, which is why I have them mapped as separate layers too.
Any suggestions much appreciated!
Caroline