Enum type TileMapAxis in namespace Saandy.Tilemapper. It defines four axis options XZ, YZ, XY and XYPlus, with Title attributes on the last two values to supply display names.
using Sandbox;
namespace Saandy.Tilemapper;
public enum TileMapAxis
{
XZ,
YZ,
[Title( "XY-" )]
XY,
[Title( "XY+" )]
XYPlus
}