There is no undo button for properties changes. Changes can be reversed but it depends entirely on what was set and how.
The mapcredentials property is a multi-value property which means the first value is defined using the xconfmanager -s (set) option and additional values are defined using the xconfmanager --add option. If you run the set option again, it wipes out all defined values. There should be at least two and usually three defined values for mapcredentials.admin.adapters.
To undo this, go to the last backup of site.xconf that included all the previously defined values. When we run xconfmanager, it creates a backup of site.xconf before making the changes. Backups are in: %wt_home%\.xconf-backup\site.###.xconf. Start with the latest and work backwards until you find the previously defined values.
Note: There are backups of the mapCredentials.txt file too in: %wt_home%\codebase\WEB-INF\.xconf-backup\mapCredentials.###.txt. However, the latest backup of this file does not include the last set value of the property. Since you overwrote the property, the backup file may include all previously set values.
Define the new xconfmanager command. We can set multiple properties at once as long as they are going to the same properties file. For example:
xconfmanager -s mapcredentials.admin.adapters="com.company.Ldap^cn=Manager^WDS_Password" --add mapcredentials.admin.adapters="com.company.EnterpriseLdap^cn=Manager&WDS_Password" --add mapcredentials.admin.adapters="com.company.testadapter^username^password" -t codebase/WEB-INF/mapCredentials.txt -p
Always set the value and then add to it. This way, we are guaranteed to always set it fresh, wiping out any old, undesired values. In this case, we can't just restore the backup copy of the site.xconf because the passwords for the adapters are overwritten when we run xconfmanager again.
This could be executed as three different commands (one -s and two --add) but in this case I like it all as one to ensure I don't miss a setting. If you discover your adapter isn't necessary, you can run the command above again without defining it or use the --remove option to remove just your adapter.