Keeping text linked to its file in Layout by Zaweba
Type > Linked text in Layout by Zaweba keeps a story tied to its Word, RTF, HTML or Markdown file, and linked copies of a story follow the original.

Copy rarely stops changing once it reaches the layout. The writer sends a revised file, then another, and each time the designer has to place it again and redo the styling and the tweaks. Linked text in Layout by Zaweba avoids that. A story can stay linked to the file it came from, and when the file changes, Layout tells you and reads it in again.
There is a second kind of link too: linked copies of a story inside the document, which follow the original wherever it changes. Both live under Type > Linked text.
Linking a story to its source file
When you bring text in with File > Import text, the story can be kept linked to its file. The file can be plain text, Markdown, RTF, HTML or Word. From then on Layout knows where the words came from.
If the file is edited and saved, the change shows up in preflight. The same happens if the file goes missing, for example because someone moved the folder. You then choose Update, and Layout reads the file again into the story. You don't have to hunt for the right frame or remember which version was placed.
This is the same idea as linked pictures. A photo placed from a file can be updated when the photo is retouched; a story placed from a file can be updated when it is rewritten. Preflight treats both as things to check before export, so a story that has changed since it was placed doesn't slip through unnoticed.
Linked copies of a story inside the document
The other kind of link is between stories. Make a linked copy of a story and it follows the original: change the original and the copies can be brought into line. Use Update to refresh them, and Unlink when a copy needs to go its own way.
That suits text that repeats. A standard disclaimer on every page of a catalogue, contact details on the front and back of a brochure, a legal line on every advert in a magazine section, or the same short introduction in two editions of a document. Edit it once and the copies follow.
Getting the timing right
Linking is most useful while the words are still moving. Once the text is final and the designer has started fine tuning the story by hand, such as fixing a bad break with a discretionary hyphen or tracking a line tighter, reading the source file again would bring the original text back and wipe those adjustments. At that point it is sensible to unlink and treat the story as finished.
A practical rule: link during drafting and editing, then unlink when the story moves into final typesetting. Agree with writers that, after that point, corrections are made in the layout, ideally with track changes on so they can still be seen.
Mistakes that cause trouble with links
Keep linked text files in a stable place, beside the document or in its project folder. Linked files on a desktop or a downloads folder are the ones that go missing.
Don't edit the same text in both places. If someone corrects a story in the layout and the writer corrects the source file, updating will keep only the file's version. Pick one place for edits at each stage.
Style the source sensibly. A Word file with proper heading styles maps cleanly each time it is read in; a file of hand formatted bold lines needs fixing every time.
Treat the preflight warning as a prompt, not a nuisance. A modified link means the words in the layout are no longer the words in the file, and you want to decide which is right before the PDF goes to the printer.
Where linked text earns its keep
Long documents gain most. A report with chapters from different authors, a catalogue whose descriptions come from a product team, an annual programme updated each year: in each case the words are owned by someone else and keep arriving in new versions. Linking lets them stay the owners of the text while you keep ownership of the layout.