Litchi CSV files are pretty easy to fabricate if you have any knowledge of VBA (Excel, Access). The Litchi CSV format is straightforward (one waypoint per line) but is a bit intimidating when all columns are present including actions. Litchi will accept a CSV with just the first two columns (Latitude and Longitude formatted as decimal degrees) or the first 3 to include altitude.
So if you can export waypoints from a GIS (eg QGIS) and load into an Excel spreadsheet (or enter them directly), you can create a very simple 2 or 3 column CSV then load that via Mission Hub and enter actions (eg. take photo, start recording etc) interactively. You can, of course, add extra waypoints, move existing ones here as well.
I agree re entering waypoints in the Litchi app. Not only tedious but can be painful when all you want to do is move the screen image and you end up adding an unwanted waypoint. I do all my mission setups via Litchi Mission Hub on a PC.
A couple of points to be aware of. You MUST set the option for straight line segments before flying. If not Litchi will take one photo at the first waypoint and that will be it - really tedious when you take several minutes to get to the first point only to find you have stuffed up.
Litchi will pause at each waypoint presumably to settle the aircraft before taking a photo. Depending on waypoint spacing this can add significantly to total flight time.
What can be even more tedious is the fact that you must set up a waypoint for each photo. If you decide you want more frequent photos you have to add extra points or start from scratch. In my case I normally fly missions for creating photo mosaics which involves flying multiple flight lines with equi spaced waypoints, normally 30 to 60 photos in all. So I have been experimenting (fairly successfully) in laying down waypoints just at the end of each line and using the interval timer to take photos every 3,4,5 seconds etc. For example at a flight speed of 10 km/hour a 3 second interval timer takes a photo approxinately every 8.3 metres, a 5 second timer every 14 metres and so on. With the Sandisk Ultra SD cards I use, 3 seconds is about the minimum you can go to get consistent results.
Using the timer this way the drone doesn't pause at each waypoint so you do have to consider ground smear. My flying is normally done at 100 metres so even with a 20 megapixel image as long as shutter speed is better than 1/200th second ground smear is acceptable.
Hope this helps.