Imported grids that can't be deleted

[GabrielaR]

I had an imported .ifc in my archicad which at one point I deleted because I didn't need it anymore. I deleted it from the Library and some of the parts I found on 3D and plans. Now I found I still have some grids imported from the .ifc in the elevation views that I can't delete. I can't open them in 3D or plan, or nowhere. They are in some "missing" layer, they can't be reserved, or unlocked, I can't make them disappear at all. 

When I open their settings this is what appears. But I can't make any change.

Operating system used: Windows

[Marc H]

Grid may be locked.  I recall having this issue with some RVT imported items.  

Once unlocked, you can delete them or edit to your new project in the Design > Grid System command.

Update: Oh, I re-read your post.  Seems like an orphaned object set.  A couple of thoughts:  Archive your PLN (into a PLA).  Might leave it behind.  Alternately, bring your project elements into a new PLN from your template.

[Raphael Theligmann]

You have openend the right settings.

Try hiding the grid line and unselecting the markers.