Yes, so long as you enter all required data for the portion of a record, you can save the record but not approve it.
For example if you complete the PR# and Vendor on a purchase request and then save it will allow it. But if you enter the PR#/Vendor and just the Key for an item it will not save. You would have to delete the incomplete item and before saving just the top portion.
If you don’t approve the record, it will remain in your Pending Tasks and you can access it and complete it at a later time then approve it to start the approval process.