Make charts editable without going in Edit Slide Layout mode

Hi, hope you can help me here

I am in the process of creating a keynote theme for our company with our new visual identity, where there will be many different templates to choose from, so that my colleagues can make a presentation based on our customized theme.

The question:

How can I create a template with a chart included, that they can add to their presentation and where they can change data in the chart WITHOUT going into Edit Slide Layout mode?

I created and designed a template with a diagram included, no problem there. But when you make a new presentation with the new theme and want to add the diagram template, you cannot edit the diagram without going into edit Slide Layout mode. That is not what I want with a template, because then the user can change the master template.

So is it possible to do what I am asking here?

Thanks in advance :-)