is an example glitch where after creating a new file ( SequencerInterval_test.x3d ) the file was initially listed and selectable on the left file listing but then disappeared from the list after returning to the glitch later. The file still exists, it just does not show up.
Adding a proper xml declaration as a first line in the file seems to maybe have contributed to this behavior but that would seem rather strange.
I still can edit in the console so not critical.
Thanks for a great service ! Andreas