Can Ever Affect Navigation Not Available?

I have a an Actor blueprint that has a child static movable mesh, that mesh, as intended, blocks things. I don’t want it to effect the nav mesh. I have read that Can Ever Affect Navigation is the option to turn off. In the scene hierarchy this option is not in the objects details. In the blueprint or details section, under default scene root there is this option, which is unchecked.There is no such option under the static mesh child. The object blocks navmesh (which I want to turn off). What am I missing?

I am also looking for this feature