If I were doing this I would first make sure the source maps covered an identical area by trimming them together in an image editor (PS, Affinity Photo, GIMP - take your pick). Then I would turn on the snap grid and import them one after the other, using the same snap points to define their extent. Once they are in CC3 you can scale them together, so keeping the alignment you've already set up.

There are probably many other ways you can do it. This is just the way I would do it.

This might help. The difference between a plateau, a mesa and a butte is one of scale alone, and mesas may be a huge range of sizes.

A plateau may be thousands of square miles in area and is usually flattish on top, while a mesa is an eroded section of a plateau that has cliffs all around it. Mesas are wider than they are tall. A butte is an eroded mesa, much smaller, and usually taller than it is wide.

This week, Ralf will be taking a look at the Character Artist add-on for CC3+ to build a character and a monster, and create a paper standee for printout.

Come along to youtube on the day to join in the live chat here:

https://www.youtube.com/watch?v=A35xcjcvKiw

Or watch it any time here on the forum:*

*This thread is not monitored during the live show, but is a place where you can chat about the event and ask questions.

Your local time for the event is displayed in the forum side bar.

Have you looked at The One Day Worldbuilder pdf included with FT? (ProgramData\Profantasy\FT35\Documentation)

I'm not suggesting that you make a whole world, but it might help you get a few ideas about resolutions and methods.

Remember that if you change the resolution on an existing world the shape of the landmasses may change quite a bit.

When it next does that to you check the command line to see what CC3+ is doing. It may be that you haven't finished a command.

There could be other causes, of course, but that's always the first place to look for clues.