Bug - Entering a note into new Gmail message won't work if text was selected
Try this: Create a new email in Gmail (rich text or plain text, doesn't matter). Write something. Then select your text and invoke the contextual menu and choose "Insert Note" and paste a prepared note.
The result will not be as expected, deleting the previously selected text and overwriting it. Instead a garbled small text snippet appears.
BTW, all is fine in this text box on the Vivaldi forum here where I'm writing my bug report now.