The short answer is no, both the standard client and the wfentrypoint (which is just a wrapper of this) are distributed compiled, they do not support "design time". The one that admits it is the Custom Client, from which we distribute an xpz to be able to modify it.
Anyway, unless you want to add a column of your own, I can not imagine the usefulness of being able to do it in design when it can be done at run time. Maybe what you need is that each user does not have to reconfigure it and automatically initialize it with a design that seems more appropriate. If it is the case, we see it, although we do not support it explicitly, I can pass on a trick that approaches the solution.
The available columns are bounded and can not be added dynamically. You can only hide or show the ones that are available. If you need other information that is not available in the columns, you should add it in the subject of the instance