I made a program in Google Apps Script that can do this. Here's the link: https://docs.google.com/spreadsheets/d/1YRylapVSejmJJiwzqwFxJvNK7_E__gSM8isaIf-XouU/edit?usp=sharinga program in Google Apps Script that can do this.
The link is to a Google Spreadsheet that acts as a GUI to a Google Apps Script. The Google Apps Script uses the Calendar API (here: https://developers.google.com/apps-script/reference/calendar/) to perform all the various functions that someone might want to do when editing an event. If you want to see how it works, copy the spreadsheet to your Google Drive and click in the menu "Tools > Script Editor"