Best answer by Anne Buit
You can already omit tasks, reports, prefilters etc. completely by using a variant. But I assume you'd want them to be available through other means (ribbon, context menu or hotkeys) and not in the bar?
You can indeed use a custom extender to configure items to be excluded from action bars.
Universal only has bars. To replace the ribbon and context menu, a new general action bar has been introduced. This action bar contains all actions, as long as the action is not made available somewhere else. For instance, by introducing a prefilter bar and task bar the prefilters and tasks will be taken from the general action bar.
I assume you'd want some way to mark some tasks to never show up in a task bar? This would return them to the general action bar.