It is interesting how knowledge disappears from the general hive mind over time. Just about every window has a menu there, it is called the "System Menu", and in the old days, this was also where you closed the program (try double-clicking the icon), the "X" button in the top right is of newer date.

Back in Win3 days it looked like a minus sign, but in Win95 it was replaced with the program icon instead.

The issues are caused by certain program controls not responding correctly to the scaling factor in Windows. It happens when you have it at anything else than 100%. Most of the dialogs should be fixed to work correctly with the scaling, but for any you find that don't work properly, feel free to report them.

Doing a map of that size isn't a problem in CC3+. But it will be a bit time consuming, a map like that is not done in an afternoon.

Since you're mentioning the isometric Schley city set, i am not convinced it will be appropriate for such a large city. I haven't tried, but the isometric sets are generally better when you can see the details a bit more clearly. Might be a good resource for mapping closeup of individual districts for example.

Personally, I am not convinced it is a good starting point doing such a large map if you are unfamiliar with CC3+ though. I recommend starting with something simpler to get some experience first, or it is likely to be overwhelming.

You might want to have a look at this live stream recording where Ralf starts making a small city. Far from the size of your desired city, but shows off the tools and techniques.

The only difference between regular image exporting and rectangular section is that after you have clicked save in the save as dialog, instead of starting the export immediately, you will be prompted (on the CC3+ command line) to pick two opposite corners of your export (by clicking your mouse in the drawing or typing in the coordinates, either works). CC3+ will then export only the parts that is within the area defined by those points instead of the entire map.

The export process is explained in detail with images in the user manual, starting on page 47.

If you are printing, there is a tiling option right in the print dialog, just set the desired scale (battle maps for miniatures are usually 1' = 5" (as long as your map is mapped to scale in the first place)) and set the horizontal and vertical number of tiles. Check page 47 of the user manual for details.

If you are exporting it to image files first, you can use the "Rectangular section" file type exports. This will cause CC3+ to ask you for coordinates after hitting save, and this way you can save just a piece of your map. Just use this to export your map one piece at a time.