WhatsApp, Slack, and many of the messaging apps introduced a send a message to yourself feature a while back. Essentially to a place to put in rough notes.
I use Signal's "note to self" as a sort of inbox for my notes system that I have on my computer. Y send the messages in the "note to self" chat, and once I process them, I add a thumbs up reaction to the message.
I also use it for sending links when I want to transition between devices