Seeing spaces, tabs and breaks in Write by Zaweba
Ctrl+Shift+8 in Write by Zaweba shows dots for spaces, arrows for tabs, paragraph marks and labelled breaks, on screen only and never in print.

Stray spaces, extra tabs and empty paragraphs are invisible on a normal page. They cause most of the layout puzzles people meet in a word processor: text that won't line up, a gap that won't close, a heading that jumps to the next page for no clear reason. Formatting marks in Write by Zaweba make them visible.
Turning the marks on
Press Ctrl+Shift+8 to show formatting marks, and press it again to hide them. While they are on, each space shows as a small dot, each tab as an arrow, and each paragraph ends with a paragraph mark. Breaks are shown with labels, so you can tell a page break from a section break or a column break.
The marks appear only on screen. They never show in PDFs and never print, so you can leave them on while you work without worrying about the final copy.
Problems the marks reveal
Double spaces are the classic. Many people learned to type two spaces after a full stop, and documents built from different sources mix one and two. With the marks on, two dots side by side stand out at once. Find and Replace can then clear them all in one go.
Spaces used to line things up are another. Columns of text aligned with spaces look fine in one font and fall apart in another. The dots show where spaces have been used, and tabs, shown as arrows, are the reliable way to align text. For anything more than a couple of columns, a table is better still.
Empty paragraphs used for spacing show as paragraph marks on otherwise blank lines. They cause gaps that move about as text changes, and they leave blank lines at the top of pages. Replacing them with spacing before or after a paragraph, set in the Paragraph dialog, gives a steady result.
Breaks explain jumps. If a heading insists on starting a new page, there may be a page break above it. If the layout suddenly changes to two columns, a section break is the cause. With labelled breaks visible, you can see what is happening and delete or move the break.
A tidy-up routine
Before finishing an important document, turn the marks on and scroll through. Look for double dots, tabs where they don't belong, blank paragraphs and breaks in odd places. It takes a few minutes for a long report and catches things that would otherwise show up only when printing.
This is especially worth doing with documents you received from others. A CV template downloaded years ago, a letter passed around an office, or a report pasted together from emails often hides a surprising number of stray marks.
Marks and other tools
Formatting marks pair well with the rest of Write's tidying tools. Find and Replace, with regular expressions if you need them, removes repeated spaces. Format > Clear formatting resets text that has picked up stray settings. The navigation pane shows the headings so you can check structure while the marks show detail.
Some people prefer to write with the marks on all the time, because it makes every keystroke visible. Others switch them on only to diagnose a problem. Either works, because the marks never reach paper or PDF.
Once you get used to seeing them, you start to write cleaner documents from the start: one space after a full stop, tabs and tables for alignment, paragraph spacing for gaps.