Hello CodeSlayerYT!
Thanks for your interest in the level editor! I have tinkered around with it a bit and it may just be, that it doesn't recognize 'level' or 'segment' as a type. Try typing 'l' or 's' instead and see, if that works and report back to me. Also, make sure you use the most recent version, as I recently updated the editor. (see end note)
However, you should not get your hopes up in regards to expansions of the editor. It is a tool I created for myself and it is a mess, which makes it hard to expand. However, I will definitely fix the loading bug either way :-)
Further note: I tried to load your custom levels, but it resulted in this error. Can you tell me the steps you took to create your customLevels.dat file? Perhaps the issue is a wrong formatting in the files. I will look into this issue :-)