Can a story be in a theme without being in an epic?

[Adam]

I have added a theme within the hiearchy configuration to sit above the OOTB levels, so I have

• Theme
• Epic
• Story
• Sub-task

For the way I'm using Epics (a big story), it is feasible to have a story live directly within a theme without being part of an Epic. However, in the plan view, I cannot drag a story to be within the theme directly, it always wants to add it to an extant epic. Does portfolio force a rigid hiearchy? What I would like to achieve is to have the plan view be able to have stories as direct parts of a Theme. I did see roughly the same question asked last week, hence stating what it is that I am trying to achieve.