I use a popup.html, including an input with type property file. After user choose the file (an excel file), popup.js will process the file,extract the student ID and grades, then store them in chrome.storage.lcoal as a json file, then send a message to content.js. The conten.js will autofill a student grade table using the chrome.storage.local content. The student number is over 120, so it is a tedious work repeating every semester.
The method I use now only works in inspect mode, or debug mode. without inspect tool, the popup windows disappear after the user choose the file.

Is there any other method to do that? (Let user store the file in a fixed directory, but not good enough)