Undelete elements

Is there a way to re-add/fill holes in the mesh where I deleted elements. I don't want to remesh the whole model as then I'll lose boundaries and discrete features etc.

The current implementation allows you to add/fill holes by connecting two meshes via nodes. This workflow works for 2D meshes only and Discrete Features, material properties, boundary conditions are lost. 

:( my model is 3D so if it works in 2D only then that means I need to go back to a very early version of my model and rebuild much of it.

Ideally, I would have made elements inactive rather than deleting them (as then I could reactivate them), but I didn't get the active/inactive data type until after I'd deleted an element and locked the mesh.

If I currently have a 3D standard saturated transient model with a free surface, is there a way to access the active/inactive elements data type without deleting elements and locking the mesh?

Inactive elements are not available for free & moveable meshes.