How should I add a unitary morphism of one object in the quiver?

[BHanZhang]

How should I add a unitary morphism of one object in the quiver? I want to add a unitary morphism $\mathrm{id}_X$ of objext $X$ like this:

[varkor]

There is an open feature request for adding loops here: #31. I have not found time to work on this recently. For now, the simplest solution is to modify the TikZ that quiver exports and add a loop in manually, though I appreciate this is not particularly convenient.