This happens when the group's recording directory is set to e.g. $HOME, which I picked as a random default that I intended to change afterwards.

RecordingsStore.restore_from_dir() recursively reads the directory's contents, which takes quite some time to finish. As the daemon does not respond to the UI before it's finished, the group is not created (or at least not shown in the UI).
Maybe RecordingReader.restore_from_dir() should not recurse into hidden directories and only up to a certain depth in the tree -- depending on how recordings are usually organized (I did not check this). Further or alternatively, the restore_from_dir() step could be done later and not interfere with initial setup.
I'm running version 0.1.22, but the relevant code does not seem to have changed afterwards.