Using ctrl-shift-D (cmd-shift-D on a Mac) to ADE in Library view will allow you to remove the association with old Adobe IDs; eg deactivate them on that PC.
Thanks. All I get from using this move from ADE in Library view is possibility to delete the authorization of my computer - not to delete IDs. ???
The authorization is the authorization for the computer to use books associated with a particular ID.
You can't deactivate an ID completely, you just deactivate it's use on a particular computer.
Once removed, you can then reauthorize the computer to use the ID that you need.