I don't think there is any way to group items in KiCAD per se.
The only idea that comes to mind is to make your front panel lines into a footprint. And then you may be constantly clarifying whether you're selecting the front panel footprint, or something else that is located within the bounds of the front panel footprint.
When I face situations like this (aligning with a front panel, or fitting a board into an enclosure, etc) I dedicate one of the "unused" layers to hold the information about the front panel or enclosure outline. I typically use the "Margin" layer, but "Cmts", or one of the "ECO" layers should work as well. Then I import the applicable *.DXF drawing to that layer, and make the layer visible when I need to place components or make measurements. At other times I leave the layer invisible so I don't accidentally select or alter some feature on it.