Screen modes and arranging windows in Paint
Cycle full screen modes with F in Paint by Zaweba and show several documents 2-up, 3-up, 4-up or in a grid, matching zoom, location and rotation.

Two questions come up constantly in image editing. How do I get everything else out of the way so I can just see the picture? And how do I look at two pictures at once? Paint by Zaweba answers both from the View menu, with screen modes for the first and Arrange for the second.
The four screen modes
View > Screen Mode offers Standard, Full Screen with Menu Bar, Full Screen and Canvas Only. Pressing F cycles through them, which is the quickest way to use them.
Standard is the normal window. Full Screen with Menu Bar fills the monitor but keeps the menus, which suits long working sessions where you still need commands. Full Screen gives the picture more room again. Canvas Only strips the screen down to the image.
Canvas Only is the one to use for judging work. A picture looks different without toolbars and panels around it; composition problems, colour casts and uneven edges become easier to notice. Tap F until you reach it, look, then tap on round to Standard. Combined with the Tab key, which hides panels, you have two quick ways to clear the screen.
Arranging several documents
When more than one picture is open, View > Arrange decides how they share the window. You can show them 2-up, 3-up, 4-up or in a grid, so several images sit side by side rather than as tabs. You can also float one document in a window of its own, and consolidate them back together.
Side by side is how you compare. Two exposures of the same scene, a before and after of a retouch, a set of product shots that need to match, or the different crops of a social graphic: all are easier to judge together than by flicking between tabs.
Matching zoom, location and rotation
Arrange can also match zoom, location or rotation across documents. Match zoom makes every open picture use the same magnification. Match location shows the same part of each one. Match rotation brings their rotated views into line.
This is what makes comparison useful. Two versions of a portrait at different zoom levels are hard to compare, but at the same zoom and position you can see exactly what changed in the skin or the eyes. When checking a batch of product photos, match zoom so you can tell whether the products are the same size in frame.
Jobs these help with
Choosing between shots: open the candidates, arrange them in a grid, match zoom and look at faces or focus. Matching colour across a set: arrange 2-up and adjust one until it sits with the other. Copying a technique: keep a reference document floating while you work in the main one. Final checks: Canvas Only, with nothing else showing.
Small things to know
Arranging changes only the windows, never the pictures. Floating a document is handy on two monitors, where it can sit on the second screen as a reference. If the arrangement becomes cluttered, consolidate everything and start again.
If you are using Canvas Only and need a command, keyboard shortcuts are still the quickest route, and F will bring the interface back.
Screen modes and arranged windows are simple features, but they change how carefully you can look at your work in Paint by Zaweba.