Skin Gallery - How to remove skin grouping

Hi,
The easiest way to achieve your goal is to fill the In-Ribbon and In-Dropdown gallery with required skins manually. To obtain all available skins in your project, use the SkinManager.Skins property. To populate the In-Dropdown gallery, handle the RibbonGalleryBarItem.GalleryInitDropDownGallery event.
Here is a sample code snippet that demonstrates how this task can be accomplished:

C#
SkinContainerCollection skins;  
       void InitSkinGallery() {  
           //SkinHelper.InitSkinGallery(rgbiSkins, true);  
           skins = SkinManager.Default.Skins;  

           for (int i = 0; i < 14; i++) {  
               int index = rgbiSkins.Gallery.Groups[0].Items.Add(new GalleryItem());  
               GalleryItem item = rgbiSkins.Gallery.Groups[0].Items[index];  
               item.Description = skins[index].SkinName;  
               item.Image = galleryImageCollection.Images[i];  
           }  
       }  

       private void rgbiSkins_GalleryInitDropDownGallery(object sender, InplaceGalleryEventArgs e) {  
           e.PopupGallery.AllowHoverImages = false;  
           e.PopupGallery.ItemClick += new GalleryItemClickEventHandler(PopupGallery_ItemClick);  
           for (int i = 0; i < e.PopupGallery.Groups[0].Items.Count; i++) {  
               GalleryItem item = e.PopupGallery.Groups[0].Items[i];  
               item.Description = skins[i].SkinName;  
               item.Caption = skins[i].SkinName;  
           }  
       }  

       void PopupGallery_ItemClick(object sender, GalleryItemClickEventArgs e) {  
           defaultBarAndDockingController1.Controller.LookAndFeel.SkinName = e.Item.Description;  
       }  

I have created a sample based on your description. Please find it in the attachment.
I hope this solution will be helpful to you. Feel free to contact us if you have further difficulties. We are happy to help you at any time.