Given the two examples, I'd prefer the attach-right option. The insert below option will have to shunt all subsequent rows down, which would be more irritating.
So long as there are only three (3) options to present, with clear and distinct icons, the interface could present just the icons right aligned over the selected bookmark entry (even obscuring the end of the name).
The one interface that currently irritates me is the cargo tab on the right panel - since Horizons. I always end up paging down modes rather then stepping though the manifest...