I’m setting training load, volume, experience, start date and events. However I never see the option to add ‘Time Off’ before going to ‘Schedule’. I’ve tried to do the same actions in the Trainerroad app on Windows and within a browser (MS Edge) and there is no change.
Its a retrospective thing (time off); build your plan builder plan without time off, then add annotations to add planned time off and it’ll adapt around it.
One of the Annotation Help Pages gives more details to expand on your link.
In a recent update to Plan Builder, TR took this bit out. You aren’t missing anything at all… As @HLaB mentions, it’s all retrospective now (you add it once the plan is on your calendar).