How long is the campaign in Synergy, and does the game also offer randomly generated maps or a sandbox mode for replayability?

I asked the same question on Steam and there I got this answer from a Synergy Dev (GPM_Leikir), maybe it is also handy for others:

Hello,

Synergy has 6 scenarios, on top of 5 sandbox maps playable in free mode as of the 1.1 update, so that makes a total of 11 maps (12 if you include the tutorial map). All scenario maps are also playable in free mode.
A scenario can take 4 to 6 hours to complete, maybe more depending on your skills or if you want to expand the city and reach a higher score after the scenario's end.

All maps are handcrafted and there is no randomly generated mode.