Which version of TimeMachineEditor should I use with a Mac OX 10.5.8?
You need a version older than the one currently released. The latest version is 4.3.2, and it requires OSX 10.9 or later. For previous versions of Mac OS X, you need another version that can be downloaded from the download page at Mac Informer.
Use version 3.0 or 2.5: http://macdownload.informer.com/timemachineeditor/download/