L isn't used. I'm not sure what it was intended for nostr:npub1hlq93jdtkfg29a8s7fqzzzh82q3pkc20rxucwt4geh6e56wk3y2qxdz5wg ? nostr:npub10000003zmk89narqpczy4ff6rnuht2wu05na7kpnh3mak7z2tqzsv8vwqk ?

R is for relay connection confirmation, authentication confirmation, NIP-46 request confirmation.

P is for pending items (usually lists out of sync or haven't been published recently).

Also the bottom bar gets the message area and the go-offline switch so it's not wasted.