Build 4.0.0.28 of xlsgen adds XLSB template mode. This template mode means you can open an existing XLSB file, make a few changes and save it back preserving everything including objects that xlsgen does not support yet in the API, for instance smart art (also known as diagrams). XLSB is now a first class citizen. After support for importing XLSB files, and saving to XLSB files, it was the next logical step but the dots had to be connected, and it was no easy task to keep everything in context and sometimes re-map and re-contextualize objects, all of which cannot be done without a powerful core runtime.

This template mechanism also works for buffers in memory rather than files.

Scenarios such as migrating XLS or XLSX files (and their variants) to XLSB files also take advantage of this feature to avoid losing objects. And vice versa, from XLSB files to XLSX files.