You could use some fast-loading editor like notepad, etc. to create your quicknote and then save the file in to a "hotfolder". (using the "hotfolder" add-on --it's much like an import folder for Evernote.)
The next time you fire up Joplin it should load the file into the note system.
I tested this. It worked. It's a bit clunky, but it worked for me.
Get Hotfolder addon here: Hotfolder Plugin