thanks

no, right now you can't change the seed for the new worlds,
but you can add mods from Spiece it up
this ones
[Adjustments] Northern Rivers removed
[Adjustments] Southern Rivers removed
[Adjustments] Map Seeds Patch 3

with this mods Anno create a different world from the same seed, because you change which island are in use.

to explain this a little bit more

Start the game without this three mods, make you settings, choose a map and play. after the game-start and before you start the first expedition to discover a new world, stop the game and add one or all this three mods. "Map Seed Patch 3" give's you a different map style, so that you have other islands like your starting map.
Also possible: start the game with this mods and deactivate the mods before you start the first expedition to discover a new world
P.S.: from my view, it's important, to discover the South at first and i do this without the "New-World-Mod". So i play a while, go to the south and start the the game later again with this mods.

Important: dont use the New-World-Mod in the campaign. the campaign has only one possible map and with this mod, you get the same map again with ditch water and all the ruins there, but not possible, to repair the ruin's there and you cannot use the place with a ruin. And you cannot use the left part from Ditch Water with the Cole- and Iron mines, because, its not possible, to remove the stone from the wall there with dymamite etc - so it make's no sense for me