You cannot delete individual clipboard items that you have added.
However, you can delete all the registered clipboards using the following methods:
- Clear the app cache
- Log out of the app
- Uninstall the app
*You can register up to 100 clipboards
Related:
Clear data on the device (Mobile App)
https://teachme.jp/8/manuals/11308841
Log in/out (Mobile App)
https://teachme.jp/8/manuals/3204696