Importing .csv files to LighterPack has always worked for me. Not sure if you’re trying to import a file directly exported from GearGrams, but have you tried opening the GearGrams .csv in Excel and re-saving it (as a .csv again of course) before uploading to LighterPack? All my .csv files have come directly from Excel.
LighterPack does not have the drag-and-drop functionality that GearGrams has. It’s actually even worse, IMO, in that when you copy a gear list, it remains linked to the original! The workaround I use is to keep a “master list” on LighterPack, then download that as a .csv and re-import it into LighterPack with a new name. Then I modify the new list for a given trip. It’s a little cumbersome, but honestly not that bad. I just like the layout/interface of LighterPack better. And I’m too lazy to even entertain the thought of switching. :)