For example, in this case, one of our clients wants these timelines merged, but they ate different things for breakfast in both timelines.
Try to merge them together! You'll notice that there will be a conflict! The time machine will leave it up to you how to proceed: you can edit the problematic item, it will show you the conflicting sections. You can keep either of the two versions - or create a combination of them! Remove the >>>, <<<, and === markers, and make a new commit to finalize the merge!
Again, let your finalized timeline be the "main" one.