I am not sure if it is the simplest widget, but the text widget is one of the simplest widgets.
It is part of every wiki but here is a link to it on tiddlywiki.com https://tiddlywiki.com/#%24%3A%2Fcore%2Fmodules%2Fwidgets%2Ftext.js -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to tiddlywiki+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at https://groups.google.com/group/tiddlywiki. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/b674fc30-cb1c-4350-aaab-80f3a3c4e8a5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.