I'd recommend creating 2 new activities. Existing activities that have been manually hidden or shown in the past or which have conditional availability associated with them will cause unusual looking (but probably correct) behaviour. Hide a section containing one or more activities. The activities should be hidden. Unhide that section and the activities should be made visible. Hide a section then drag a visible activity into the hidden section. The activity should be hidden. Drag the activity into a visible section and it should be unhidden (assuming the activity wasn't manually hidden or hidden due to conditional availability).