Submitted as FB13434700 using the Feedback Assistant.

The tip about the target keychain really saved my bacon. I was trying to get the Root Certificates for Charles Proxy installed and only received error code -25294 when using its default "Help -> SSL -> Install Charles Root Certificate" option. I then exported the root certificate as a PEM file and tried importing it manually and got the same error. Upon reading this post, I realised there was a almost hidden option I had not taken into account: (This is using Norwegian language settings, so "Valg" means "Options"). Pressing that gave me the options of Local objects (preselected) logon System Choosing system seems to have worked. Charles Proxy is only listed as supported macOS 10.15, so no wonder.