The Cut Plane component of Spaces is turned on in the Reflected Display Configuration/Reflected Display Representation Set/Display Representation, but in a quick test I see that the Space Component appears to be hiding under the Walls and is therefore not selectable as a boundary when using the CEILINGGRIDADD command. There are a number of approaches you could take to make selecting a Space easier; you will have to decide which works best for you.
1. With the Reflected Display Configuration and a Top view direction current, you could temporarily turn on the display of one of the hatch components, such as the Cut Plane Hatch, for the Reflected Display Representation for Spaces at the drawing default level, using the Display Manager or the Display tab of the Properties palette. (For the latter, you would have to use a crossing window to select both a Wall and a Space, and then deselect the Wall.) When finished placing grids, you would then have to turn this component off. This might be acceptable if this is not a very frequent need, but would likely become tiresome under most normal workflows.
2. You could make a copy of the Reflected Display Representation for Spaces and turn on one of the hatch components in that Display Representation (for this example, naming the copy Reflected Working). You would then need to make a copy of the Reflected Display Representation Set (call it Reflected Working) and edit the copy, turning off the Reflected Display Representation for Spaces and turning on the Reflected Working Display Representation for Spaces. Finally, make a copy of the Reflected Display Configuration (called Reflected Working) and edit it to use the Reflected Working Display Representation Set for the Top view direction. Use the Reflected Working Display Configuration when adding grids; use the Reflected Display Configuration for plotting or when you do not want to see the Space hatch. The advantage here is the end user only needs to change the Display Configuration, and since your customizations are in uniquely named display settings, it may be easier to migrate them to future releases.
3. You could edit the Reflected Display Representation for Spaces to both turn on one of the hatch components and assign it to a specific layer. That would then give you layer control over whether or not the hatch is visible. If you make that layer non-plotting, then you would not need to worry about it being left on in a plotting view.
So far as I know, there is not a command to toggle the display of one of the hatch components of Spaces. like there is for the justification display of Walls.
David Koch
AutoCAD Architecture and Revit User
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