Hello, fellow Annoholics!
Before starting this discussion, let's not forget the recent news about the future of Anno 1800: (https://anno-union.com/union-update-whats-next-for-anno-1800/). In short, there won't be a full season from there on as the team will be working on a new project, however the team "still got a few things planned for [this] year". So I'm not expecting anything, but am rather curious what would the community think of it!
Mind you, I am nearly clueless about programming and such. While I do understand simple lines of command, I have no idea what amount of work would that take to create one. Probably too much trouble if it weren't a tool created from the start to let the team work with, but I can't forget the great experience I had with a RTS I'll avoid naming nearly 20 years ago (creap, already?!) which offered it to players, and kept the game alive through its community for several years (the brand became a MMORPG today).
According to a short topic about a map editor (and Ubi-Thorlof's answer), several third party tools are used to develop the game, making something even more complex unfeasible. Yet if it were a topic for the next Anno iteration, would you be interested as a player in a tool that lets you start from scratch a complete scenario, creating out of thin air your own islands, setting up your fertilities/mines/wells, defining scripted events & triggers to have your scenario take place, and so on? If you never got to try one out though, it's "work" (sounds less like it if you really enjoy it) that takes several dozens of hours.
While I enjoy Anno 1800 as-is, the one thing I miss the most would precisely be such a tool. I discovered the brand with 1404 and that really stuck with me - the sandbox is great, but even if you can set definite objectives to end your playthrough, sometimes you long for a less complex gameplay to toy around with for a shorter gaming session, to tell a tale of your own. Even moreso as our current examples in 1800 provide fresh mechanics that differ from the sandbox, so you get ways to differently enjoy once more your (at least my) favorite game. I've been especially longing for another Barrens scenario in the Arctic, but that's personal taste and it's (very) unlikely; should a Roman times Anno get out though, now I'd be starving for a scenario editor as it's more of my kind of historical period (I mean, half of my books are about the Greek/Roman times).
So the question stands: if it could be created, would you be interested in a complex tool, which after many hours of commitment (probably something worth several months to the average working person) lets you create a scenario of your own to tell a story of your choosing? I know I would!