It would be convenient each formula to have a description underneath. In this case, the user can choose the most suitable one for a certain case, without the need to know all formulas in advance.

Provide a more descriptive and structured way to present the built-in formulas. The formulas can also be grouped by type and visualized as a list.

The status bar is used to represent a summary of the aggregated values of the selected cell.

Provide built-in border tools for customizing the appearance of the cell borders. A similar feature is already available in the Kendo jQuery Spreadsheet:

Allow creating custom toolbar tools in Spreadsheet.

Allow the developer to customize the built-in Toolbar actions in Spreadsheet. Provide the ability to reorder or show only part of them:

Provide a readonly property to prevent the user from interacting with the data inside. 

Consider allowing the user to download the sheet.