Starting in 4.27 additional modes should be supported - per-actor, per-material, per-primitive (current), per-folder, or per-layer (with some limitations, it only takes the first layer an actor belongs to). This adds some additional detail to the ids compared to current (as we now support per-material for each component, instead of the component as a whole).
Make sure you check out the documentation on re-creating Depth of Field and Motion Blur in post processing software (Nuke) since they are still not supported by the pass directly!