This extension adds a 'Duplicate event' icon on the event preview card, letting you quickly duplicate it with one single click. You can also quickly duplicate an event by holding alt (option on Mac OS) while clicking the event. --- Source code: https://github.com/fabiosangregorio/google-calendar-quick-duplicate
You can Follow the below Step By Step procedure to install the Google Calendar Quick Duplicate Chrome Extension to your Chrome Web browser.
It is the Google Calendar Quick Duplicate Chrome extension download link you can download and install Chrome Browser.
On Google Calendar... Sunday, Saturday, Today, and other weekdays, You can select the text color and background color.
More events. Less toolbar.
Shows event durations on Google Calendar.
Mark events as completed or cancelled in Google Calendar with emojis or strikethroughs.
Hide morning hours on your Google Calendar to stop wasting space on your screen for empty hours.
Colorize events in the new Google Calendar. (Keywords: Gcal color colors event)
Adds more colors to Google Calendar!
Displays time spent on each of your Google Calendar colors!
Extra Options for Google Calendar