Does your model necessitate associating a story to a theme straight away? Ideally I would want to be able to create stories. Once I have a list of them I would look a the list and work out which theme to put them into.
If you automatically put them into a generic theme then it seems like unnecessary steps are involved since I would then have to change the theme or move stories to a different theme when I am ready.
If it is difficult for you to not link to themes then I can live with Add button associating stories to generic theme but I would suggest that most people using this product will hit the same issue which is they are not quite ready for themes when they are adding stories. Most of the time my stories come from workshops and they are captured without thought to theme since the Business stakeholders generate them. I normally capture them as a mind map and then add them into a system. It is only at this point that I can look at grouping (theme) them.
If it is difficult for you to not link to themes then I can live with Add button associating stories to generic theme but I would suggest that most people using this product will hit the same issue which is they are not quite ready for themes when they are adding stories. Most of the time my stories come from workshops and they are captured without thought to theme since the Business stakeholders generate them. I normally capture them as a mind map and then add them into a system. It is only at this point that I can look at grouping (theme) them.