Something I use for keeping track of what tiddlers i have folded so I can selectively unfold them without using unfolding all (my method of madness involves having tiddlers folded that end users needn't worry about viewing)
<$list filter="[prefix[$:/state/folded/]text[hide]] +[removeprefix[$:/state/folded/]]">
<$link><$view field='title'/></$link>
</$list>