Hi @Eaven HUANG ,
Welcome to our forum!
As I know, we can move the items in personal calendar to shared calendar directly. For specific steps, please refer to:
1.In calendar view, select your personal calendar.
2.View>Change View>choose List.
3.Press Ctrl + A and right click, choose Move>Other Folder… or Copy to Folder>choose the folder you want to move.
Hope the above help!
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