Enhance Google Calendar with https://www.calendarcombinator.com to sync events between calendars.
Extend Google's calendar to let you sync events between Google calendars you have set up in Calendar Combinator.
1. Sign up to https://www.calendarcombinator.com and install this extension
2. Within https://www.calendarcombinator.com:
* Add at least 2x google calendars
* Create a 'selected' combination
3. View your source calendar at https://calendar.googe.com
4. Click on an event and you'll see buttons to select events to sync to the target calendar