Legends has at least a loose chronology for the development of Coruscant.
200,000 BBY: Local urbanization
As of this time, the ancient Zhells had at least one city. There were still natural features such as volcanoes, however, and urbanization had not yet reached the point it had some tens of millenia later, when nearly the whole surface was covered.
According to a blog post about material that was considered for Star Wars: The Essential Guide to Warfare, but was never included:
The outlines of what happened some 200,000 years ago are known to
every schoolchild: The 13 nations that made up the Battalions of Zhell
spent centuries clashing with the forces of the Taungs. During one of
their skirmishes, a volcanic eruption destroyed the city of Zhell,
shattering the Battalions’ power. The assembled Taungs watched in awe
as ash blotted out the sun and rained down upon them. Taking their
opponents’ destruction as a sign of divine favor, the Taungs
christened themselves Dha Werda Verda, the Shadow Warriors, and
celebrated their victory in the epic poem of the same name.
90,000 BBY: Significant global urbanization
In murky prehistory, the planet that would become Coruscant served as
a battleground between the Taungs and the human tribes of the
Battalions of Zhell. The withdrawal of the Taungs to Roon left humans
in sole possession of the world, and urbanization soon followed. The
megalopolis that would one day become Galactic City is said to have
already stood layer upon layer as early as 90,000 BBY.
Sometime after 30,000 BBY: Planet-wide urbanization
The planet was not entirely urbanized until 30,000 BBY at the very earliest. This is when the Infinite Empire of the Rakata took over:
The Rakata of the Infinite Empire assumed ownership of Coruscant in
30,000 BBY, providing technical clues that allowed the Coruscantis to
build sleeper ships and colonize habitable worlds over the course of