Welcome on-board!

The advice from everyone above is very sensible, and should help you get started.

The main problems I found early on with the software related chiefly to being more familiar with how desk-top publishing and graphics manipulation software works, whereas CC3+ is genuine CAD software, which works in a very different way. Equally though, it's also far more powerful and - once you get into its apparent quirks - far more useful.

I found the Joe Sweeney videos the most helpful, as I started with CC3, but the more recent videos (which didn't then exist) for CC3+ by Ralf (the live mapping streams) and Remy are just as useful.

Best advice is once you're familiar with the basics, through video tutorials and/or the Manual, just make some maps of your own, and learn from that - including making mistakes, and working out (or asking here!) how to correct them. Good luck!

Not sci-fi, since they were all done for the Nibirum Community Atlas, which is all fantasy mapping, but they were done in the general style of planetary-system mapping, so may still be of interest. However, I did a series of maps for said Atlas back in 2018 - Forum thread here, Nibirum Solar System start page here, with a sample map to give you an idea, just for the inner planets:

All these maps are also in my Forum Gallery here.

Here we go again (hopefully with better luck this week though!)...

Sorry, Frosty, I don't.

However, a quick check online shows there are at least two CC3+ maps of the Isle out there, both from 2022. One is by Jason Hibdon, on the Atlas of Mystara website, the other is on the Talaraska blog. In neither case is there an FCW file provided, but it couldn't hurt to contact the people involved and ask nicely!

I'm not sure if either may be on this Forum, or perhaps the Cartographer's Guild, as well.

Just a thought, but did you set up the trees so you can hide the canopies, yet still show where the trunks are for use in ground combat? Of course, that also means you can hide any GM-placed traps under the canopy cover as well 😉!