Apply proper header styles

[matt-dray]

The guidance says that sheet titles should be header H1. I can't see how to do this in {openxlsx}.

Also not sure if Excel can actually distinguish between simply adding H1 markup vs H1 style.

I think you apply H1 by applying it as a style, as per the Home > Cell styles menu:

It's possible that marking-up the cell will invoke the 'H1 cell style' that's default in Excel, which we don't want.

(Thanks for the reminder of this, @phil-hall-moj)

[matt-dray]

Also H2 headers to the subheadings on the cover page, for example.