Using Markers you can export only a part of the Timeline (export as a video, I mean). But this doesn’t work to Save only a part of the Timeline as a MLT file.
Also, ShiftI and ShiftO (or just I and O) are shortcuts used to trim individual clips, not to trim the Timeline.
If you want a MLT project with only those Logan clips, just create a new project, import the Logan clips in the Timeline in the order of your choice and Save that project.