You are right, OOo is limited in this domain. You can only do basic insertion/deletion: position yourself on the contiguous row(s)/column(s) you want to insert/delete and then right click in the selected area to perform the action.
You cannot insert rows/columns when there are merged cells. You cannot "insert then copy" like in Excel. I think I have seen an add-on that extends the feature, let me do a quick search on this...... Here it is! http://extensions.services.openoffice.org/node/1798