I would have an idea or two to simplify the work of many SMB3 hackers, in the meantime you could certainly put in the map editor menu an option to enlarge the window by x2, x4, x6 times in order to provide a good map view, but yes could include in the software editor map a fiction that takes into account the size of any internal world of SMB3 so even if its Hex code were modified in these parts and you could also choose, through selection tips in a window, if the parts are divided like world 8 or 5 and or if they are bleak as in the third part of world 8, you could create a set for the size of a world you are in (find according to the chosen world in the map editor menu)
and precisely meaning how many map screens can be displayed linked or divided for that world, you could have a window with miscellaneous settings to set the colors by choosing the desired palette, both of objects and sprites, even having the possibility therefore to change the colors of the world 9, why should I do this with other programs like FCEUX if I am working with a map editor? The miscellaneous settings could include specific things about the map, such as a quick change to the map sprites via a dedicated window, such as skulls, fire, bushes, just to change the face of the map quickly and easily, to make it so a really good map editor, apart from all the Mario colors could take into account they are set
in the Hex code for little Mario when, for example, you move the starting point in a world in the map editor or in the Viwer function. Also in the miscellaneous part you could change the colors of the external bottom bar of the layers, even if it is not seen in the map editor, having the opportunity to change the external and internal color and the color of when it turns or changes group objects. You could also add a setting in another part of the menu to establish the three starting points of mario in world 9 if you are editing world 9 (Warp Zone) and where they must be in the map, thus being able to change the three points via buttons page up and page down, then also, with another dedicated function, also the visible numbers that label the tubes that will lead to the worlds, and if possible, adding a dedicated set in the miscellaneous options window, to be able to remove them permanently, this also seems to me a setting that should be there.
Certainly, however, a small new software could also be created for a special modification, to easily change the final scene, its colors such as curtain colors, and the whole final environment, for example instead of making the various maps appear in small format in the scrolling of the final scene, you could give the option to write custom credits to write special thanks or Mario's ending story with the princess. Finally in the software options choose as game setting, which objects to give at the end of the SMB3 game for a new game after finishing one, change the P-wing (original set) with another object or include the choice of colors in sequence. Door ring leads to Princess in Browser Castle.