@cqroot, I can't replicate the issue but I think it's partly due to the use of a deprecated function call here: joplin-outline/index.ts at b59c68f9e44eafec94c9e2274068afba5ca17b0d · cqroot/joplin-outline · GitHub
Normally an ID should be provided so that the app can know what panel corresponds to what plugin across restart. Currently it if doesn't the app should set a default ID, but for some reason it's not happening here.
I'm going to fix it anyway so that the app doesn't crash when the ID is undefined, but you might want to set an ID as the function call without an ID will stop working from the next version.