One option -

Collapse the sheet to show only the subtotals, then select visible cells
only (F5SpecialVisible Cells only)

Then Bold those cells and, instead of adding empty rows, make the subtotal
rows taller and format them with the vertical alignment at the top


"slh" wrote:

When using Data, Subtotals to create subtotals in a detailed spreadsheet,
how do I set the format so that all subtotal lines are bolded and are
followed by a specified number of blank rows?