Quick solution: If you do not need the "Pop-up window with video" function, you can close the "Extension: Video handler" process in the Opera task manager. (You will have to close it 2 times). The problem "Ctrl + Shift + Del" will disappear. Valid until browser restart.
Possible solution for experienced users only! : Close Opera browser. Using JSONedit, delete the section "extensions" - "commands" in the Preferences file in the profile.
After that, you can use the keyboard shortcuts "Ctrl + Shift +" in third-party programs when Opera is running and "Ctrl + Shift + Del" to delete the history in the current Opera 63 Stable.