My workaround for this problem is to make a separate level for each datasmith import, and then use level streaming to bring each level into a master level. Then, if I want to delete the entire datasmith import, I can remove that level from level streaming, close unreal, and delete the level and folder in windows explorer (NOT in Unreal). As long as there are no references to the imported assets in any other level, unreal will be perfectly happy when you reopen the project.
It’s not a perfect solution, as it can lead to a lot of streaming levels, and only works if I want to delete the entire import. I tend to only do it for large datasmith imports in early design phases.