public bool IsVisible {get; set;}

//var voxelLayer = ... ;
//Must be on the QueuedTask.Run()

if (voxelLayer.Visualization != VoxelVisualization.Surface)
    voxelLayer.SetVisualization(VoxelVisualization.Surface);
voxelLayer.SetLockedSectionContainerExpanded(true);
voxelLayer.SetLockedSectionContainerVisibility(true);

var locked_sections = voxelLayer.GetLockedSections().Where(ls => !ls.IsVisible);

//Make them visible
foreach (var locked_section in locked_sections)
{
    locked_section.IsVisible = true;
    //apply change
    voxelLayer.UpdateSection(locked_section);
}