This is a bit of a silly shortcut; you would never actually want to automate this! But it demonstrates how to apply a mass change to the events in a timeline. It’s based on the assumption that you are mid-project and just realized you need another week. It locates every event which ends after today; if it’s already started, it extends it by one week; if it hasn’t started yet, it slides the event start out by one week.
Before:
After:
Download from this iCloud link.
Here's how it looks in the Shortcuts app:
