Hello,

Would be useful if I could hide/unhide a worksheet. Currently couldn't see an option to do so.

Maybe as some property:
var sheet = workbook.addWorksheet('My Sheet', {properties: {hidden: true}});

Along with some function to check hidden status
workbook.getWorksheet('My Sheet').IsHidden(); // true or false

And to also toggle hidden status on the fly:
workbook.getWorksheet('My Sheet').hidden = true; // or false...

Would also be useful to re-order sheets in the workbook programmatically. I guess you could technically just "add" sheets in the correct order then circle back around and add data as necessary... but reordering sheets would allow you to not need to do that.