Adding multiple rows/columns to a spreadsheet in Calc

From NeoWiki

Inserting more than one row/column at a time

• To insert multiple rows/columns into a Calc spreadsheet at one time, select the same number of rows/columns as you want to add, beginning at the row.column AFTER where you want the insertion to be, then ctrl-click/right-click and choose Insert Rows/Insert Columns from the contextual menu - or click on the Insert Rows/Insert Columns button in your toolbar if it's visible there.