Outline view, pixel preview and view modes in Vectornation
Outline view (Ctrl+Y), Pixel preview, Trim view, Presentation mode (Shift+F) and screen modes in Vectornation by Zaweba, and when each one helps.

How you look at a drawing changes what you notice. Vectornation by Zaweba gives you several ways to view the same artwork: Outline view, Pixel preview, Trim view, Presentation mode and a choice of screen modes, including full screen with the menu bar. None of them changes the artwork itself, but each one helps with a different job.
Outline view
Press Ctrl+Y for Outline view. Fills, strokes, effects and colours disappear and you see only the paths, as thin lines. It sounds stark, and it is, but it shows things that the normal view hides. Stray points left over from editing, shapes hidden behind other shapes, duplicate paths stacked on top of each other, open paths that look closed, and tiny fragments that will trip up a cutter or a printer all stand out at once.
Outline view is also faster to work in on very heavy files, and it makes selecting easier when a busy illustration has lots of overlapping shapes. Press Ctrl+Y again to go back.
Pixel preview
Vector artwork is sharp at every size, but much of it ends up as pixels: web graphics, app icons, social media images. Pixel preview shows the artwork as it will look once it is turned into pixels, so you can see where a thin line will blur across two rows, where curves will look jagged and where small type will smudge. For icons and interface pieces especially, check in Pixel preview at 100% before you export, and nudge edges so they land cleanly on the pixel grid.
Trim view
Trim view shows the artwork trimmed to the artboard, as it will appear in the finished page, without anything that spills over onto the pasteboard. Artwork that bleeds off the edge and objects parked beside the page vanish from view, leaving only what is inside the page. It is a quick way to judge a composition the way a reader will see it.
Presentation mode and screen modes
Presentation mode, on Shift+F, shows the artboards on their own, without panels or tools. It is handy for showing a client a set of designs on your screen, or for stepping back from your own work to see it fresh. The screen modes choose how much of the interface stays visible. Full screen with the menu bar keeps the menus within reach while giving the canvas the whole screen, a good compromise on a small laptop display.
A routine that uses them all
Draw and edit in the normal view. Switch to Outline view every so often to tidy stray points and hidden shapes. Before exporting images, check in Pixel preview. Before showing anyone, look at the work in Trim view or Presentation mode. Each check takes seconds, and together they catch most of the small faults that make work look unfinished.
One caution: it is easy to forget you are in Outline view and wonder where your colours went. If the drawing suddenly looks like a wireframe, Ctrl+Y brings it back. Likewise, if the panels have disappeared, you have probably switched to Presentation mode or a full screen mode, and the same shortcut or the View menu returns you to normal.
Changing view is free and instant, so use it often. Seeing a design several ways is one of the simplest habits that separates tidy work from merely finished work.