The method should create deep copy of  the current page.

Add support for array formulas (CellFormulaType "array"). These formulas can accept as parameters and return results containing whole arrays (one- or two- dimensional) of data. In MS Excel, such formulas are inserted with CTRL + SHIFT + Enter, and visualized enclosed with curly brackets ('{' and '}'). 

It would be nice to have the ability to search text in documents.

Use case:
I needed to replace some keywords with images. I can insert image at the current position, but there is no way to insert it after some text.

Provide a way to export filters.

Here is a sample structure of the signature: 

/Type /Sig
/SubFilter /adbe.x509.rsa_sha1
/Filter /Adobe.PPKMS

The DataBinding property tells the editor to show the linked content instead of the actual runs in the content control.

Duplicated with WordsProcessing: Add support for content control values that use data binding.

Text frames are paragraphs of text in a document which are positioned in a separate region or frame in the document and can be positioned with a specific size and position relative to non-frame paragraphs in the current document. More information about it is available in section 22.9.2.18 ST_XAlign (Horizontal Alignment Location) of Open Office XML.

When a chart is created with RadSpreadProcessing, by default it is exported with legend showing category list. If an xlsx file with a chart with legend showing only series is imported and exported, it will be changed to category list as well. API to switch between the two should be added.

Legend showing category list:

Legend showing series: