The following code offered by ccstone has worked marvelously since 2017 to capture text in a variable that indicates whether a file attachment has finished uploading in a Chrome Gmail. It no longer seems to get "Attachment %Variable%Message_Filename% added." text where I use the variable Message_Filename for whichever file is being attached.
The text now found in the Chrome_VisibleText variable seems to hold my Gmail labels and other text from the main screen (e.g. the body of the message that the file is being attached to).