There really isn't a "one-click" or way to do that in CC3, but Valarian's suggestions are what I would suggest as well.
First, I'd create several pre-defined zoom views (called 'view sets' in CC3) in the FCW map file, such as "Island Closeup" for example. More info on view sets here.
I'd probably then create additional layers that could be visible or hidden, depending on the view. For example, I'd put the world view size text on a layer Text Labels, then create a layer called Text Labels2, and put text at a smaller size appropriate to the zoom in level on that layer. On a zoom in, I'd hide the Text Labels layer and keep Text Labels2 visible. I'd do the same for the various settlements - put the major metropolitan areas on the Structures layer, and create a second layer called Structures2 to put all the smaller settlements. You could even vary the symbol size on that second layer to something appropriate for the zoom (including smaller versions of the symbols, even for the large metro areas, since the larger symbols would not be visible when you hide Structures and make Structures2 visible).
It gets more complex if you are using sheet effects, since these effects can look really nice at one zoom level, but need to be tweaked at another zoom. The principle would be similar to what you would do with layers above, and work in tandem with that.
None of which is very convenient or elegant in play, and certainly not "one-click"...
I haven't really use macros either, but maybe there is someone out there who can expand on this idea to make it more efficient in play with a macro.
I'm not very familiar with FM (Fractal Mapper, right?), but that feature as you describe it would certainly be infinitely useful in CC3, especially as the software matures and evolves in the virtual tabletop era. It would be awesome if CC3 view sets had an option to retain visible and hidden layer and sheet info when you select them, as well as sheet effects on or off. I'm going to point this thread out to the folks at Profantasy.