Currently the API allows ClipboardHandler-s to be registered in ClipboardEx.ClipboardHandlers collection, which is used when content is pasted. 
We can extend ClipboardHandler with property describing whether the handler is supported for copy, paste, or copy&paste, and use the collection for copy operation as well.

Workaround: Use RadRichTextBox.CommandExecuted and on copy, enhance the original data object in the clipboard:

            this.radRichTextBox.CommandExecuted += (sender, e) =>
            {
                if (e.Command is CopyCommand)
                {
                    var originalDataObject = Clipboard.GetDataObject();

                    DataObject dataObject = new DataObject();
                    foreach (string format in originalDataObject.GetFormats())
                    {
                        dataObject.SetData(format, originalDataObject.GetData(format));
                    }

                    dataObject.SetData("Html", new HtmlFormatProvider().Export(this.radRichTextBox.Document));

                    Clipboard.SetDataObject(dataObject);
                }
            };

Implement generating of an image and inserting it into the clipboard on copy/cut so it can be pasted in MS Paint or other tools for image editing.

Attaching to the CommandExecuting event of RadRichTextBox and handling the copy command can be used as a workaround:
CopyCommand command = e.Command as CopyCommand;
  
if (command != null)
{
    ImageInline image = this.radRichTextBox.Document.Selection.GetSelectedSingleInline() as ImageInline;
    if (image != null)
    {
        Clipboard.SetImage(image.ImageSource);
        e.Cancel = true;
    }
}

When the caret position is inside Table and a page break is inserted, the table should be split into two tables with a page break between.

Expose an API allowing easy customization of the layer.

Currently, working with bookmarks and cross references in the headers and footers of a document is not supported.

Currently, when the users perform replace, and there are no more matches which should be replaced, the "The searched text was not found" message is shown. Add functionality to say that there are no more matches instead of saying that the text is not found.

Provide option for configuring the measurement units (centimeters [cm], inches [in]) used throughout RadRichTextBox UI, including:
- Ruler (currently supported and configurable through DocumentRuler.MeasurementUnit property which is of type UnitTypes)
- Table dialogs - for indents, widths and heights
- Paragraph indentation (currently shown only in points [pts])
- Section properties - header from top and footer from bottom
- Page setup - columns width in Columns dialog
- Page Margins and Page Size in Ribbon UI

Currently parts of the dialogs and controls shows measures in pixels (actually DIPs), other in inches (e.g. ruler).

Provide option for exporting InlineUIContainer and FloatingUIContainer as images to docx and RTF format.

Implement advanced find dialog similar to MS Word which provides an option to search for paragraph end marker, tab character, and others.

This includes resizing, rotating and moving. Consider implementing the full functionality for interaction with both floating and inline images. 

This element specifies a set of table properties which shall be applied to the contents of this row in place of the table properties specified in the tblPr element.

In RichTextBox, only the background (the fill attribute) is supported and the val and color attributes (determining the pattern and its color) are not respected while importing.

The attribute is currently not supported when importing HTML documents. It can be replaced with the corresponding CSS property applied to each cell of the table.

Consider introducing a property in the XAML that allows the user to set whether the gallery should be loaded asynchronously or not in order to handle scenarios in which the TableStylesGallery is not in a contextual tab.

Improve the performance when a document is printed.

This includes everything related to:

- Navigation of the controls only with keyboard (Tab, Shift+Tab, arrows, Alt+<Letter>)

- Correct Screen Reader pronunciation when entering into/navigating in the control, including RadRichTextBox itself. 

Currently list styles cannot be removed from the document model.

There is no command or API in the editor for deleting paragraph, but there is such for, for example, deleting table. 

In MS Word, the users can change the background color of the page. 

A 'w:background' property is applied to the whole document in DOCX, and this property is used as a page color in Paged layout mode, and as a background color in Web layout mode. 

When implementing, think of whether RadRichTextBox.Background should be synchronized with this property when RadRichTextBox.DocumentInheritsDefaultStyleSettings is true.

Workaround: Currently, background could be set using RadRichTextBox.Background property in Web layout mode, and using a custom style, as described in When the LayoutMode is Paged the Background forum thread, in Paged layout mode.