Inserting a row in OpenOffice.org Calc is easy. Let's say you've made this schedule and you need another row because you need more slots for night life.
Right-click on the row below where you want the new row to appear, and choose Insert Rows.
Bam, you get a new row. Now you have two blank ones so if you decide you need even more new rows, you can select two rows, choose Insert Rows again....
and then you get two more new blank rows.
That's the way I've always done it.
But then I had a brainwave -- you don't have to select blank rows in order to insert rows. That is, if you want to insert three new rows, just select three rows, period, whether they have content in them or not. Then as usual right-click on the row headings and choose Insert Rows.
and you get your three new rows, above the rows that you selected.
I'm not sure how I got stuck on the idea that you have to select blank rows if you want to insert multiple rows at a time. But you don't. So here's the summary.
If you want to insert multiple rows, just select that number of rows, right-click on the row headings, and choose Insert Rows. Doesn't matter if there's content in the rows that you select; the content won't be affected by the Insert Rows action.