The separator feature in the Gantt chart should work as the first line. The following code does what you would expect if the first separator is commented out. With it in, no diagram (nor error) is generated.
@startgantt
-- Initialization --
[Config Routing Fabric] as [cfg_rte] lasts 73 days
[Init Counters] as [cfg_ctr] lasts 4 days
[Init Decay Ctr] as [cfg_dec] lasts 1 days
[cfg_rte] -> [cfg_ctr]
[cfg_ctr] -> [cfg_dec]
-- Run Time --
[foo] lasts 3 days
then [bar] lasts 5 days
@endgantt
