I use two OmniOutliner files. In one, Packing Supply, I have a list of everything I might ever want to pack. It’s organized with headings such as “Dress outfits,” “Casual stuff,” “Stuff I need in the hotel room.” The second OmniOutliner file is called Packing Checklist. In that one I write a series of headings such as “Day 1, Fly There. Day 2, Attend Meeting. Day 3, Hang out. Day 4, Fly home.” I open the Packing Checklist on the left side of the screen and the Packing Supply list on the right, then drag and drop from right to left. That way my master list of anything I might consider remains intact, and it’s very easy to update it with new ideas, get rid of stuff I don’t want to consider any more, etc.
If you want to get fancy once you have dragged everything you want into the Packing Checklist OmniOutliner file, you can add some checklist columns – does it go in my carry on bag, in checked luggage, or will I FedEx it? (Or will use DUFL.com? – check it out – if you travel a lot it’s a great service. They store your stuff and you indicate what you want them to send ahead of you by FedEx). Then you can filter the view to show the stuff according to how it’s going to get there, if that’s an issue.