Often you need to be able to do a quick edit or spell check. A lot of web applications — Grav and NextCloud, for example — use markdown syntax, and prioritize formatting over spelling. So Browsers the inbuilt spell checker doesn't work, so a quick spell check can be useful.
Other applications — word processing applications, for example — can make it difficult to past text into documents without importing the formatting from the source document. Pasting into and then copying from a basic text editor can remove the formatting.
Fortunately you don't need to leave your browser. Paste the following into the browser address bar will give you a workable text editor.
data:text/html, <body contenteditable style="font: 1rem/1.5 monospace;max-width:40rem;margin:0 auto;padding:4rem;">
Hit F11, and you have a full screen, distraction free text editor that will let you concentrate on your words. You can play about with the page style if you want - you could have
data:text/html, <body contenteditable style="color:555555;background-color:222222;font:0.5rem/1.5 monospace;max-width:40rem;margin:0 auto;padding:4rem;">
if you fancy yourself as a designer :-)
Hit F11, and you have a full screen, distraction free text editor that will let you concentrate on your words.
Bookmark the page for future reference.
One of the main reasons I like this idea is that it is a quick way to remove formatting. Unfortunatly the bookmark above does not do that, so here is another one. And for some reason, the 'target="_blank"' isn't working, so you need to right click on the link, and open in a new window.
data:text/html, <title>Editor</title><body style="background-color:silver"><div style="margin: auto;max-width: 40rem;"><textarea style="font: 1rem/1.5 monospace;width:100%;height:100%;padding:1rem;"></textarea></div></body>