I did some further reading last night. One answer that I read was I have a version of 1803 (insider) that wasn't released for the general population, it was an insider version and MS suspend the app for reasons of saving power. The green symbol is the econo symbol. I have never belonged to the insider group, the 1803 version I downloaded from the catalog.
I was wondering what it was.
It often appears against Edge. Expanding Edge shows the symbol against suspended webpages.
Maybe this is MS's answer to all the criticism of Edge eating/leaking memory.
Another backdoor 1803 feature