Organising elements on the timeline both chronologically and hierarchically is very intuitive. There are only a few considerations and norms to bear in mind.
Just like dealing with any timeline that combines elements of different nature on a same space and time, the priority of such elements when it comes to visualise them is defined by their hierarchical ordering. If two or more elements overlap in the same canvas coordinates, in the same time code –same place, same time–, giving priority to the element of which layer is upper solves the conflict. Therefore, in order to change priorities and avoid possible hidden elements, you have to pay attention to layer ordering.
Changing layer ordering is as simple as clicking and dragging every layer you want to move.
Tip: To make a multiple selection, keep pressing the Shift key while you select all the elements you want to delete all at once.
Likewise, to relocate an element of the timeline, simply clicking on it and moving it left or right will do. If you want to read more about the position of elements along the timeline, you can have a look at the article Define entry and exit points.
If you are already familiar with any editing software, you should also be aware of how a timeline is functioning. PlayFilm's timeline differs from the traditional software in the lack of the obligatory consecutive order of the elements placed in it. When placing videos on timeline there's no need to organise them by their playback order. Therefore, PlayFilm's timeline allows make "jumps" from one video to another without considering any separation or order in between them. It works pretty much as the Marty McFly's Delorean from the "Back to the Future" trilogy.