Usually only programmer editors and IDE's have that feature, usually termed as 'Fold' or 'Collapse'. And generic editors enable it only on known sourcecode types, like .c, .cs, .java, .ahk, etc. where the structure of the content is known, and can actually be collapsed in useful chunks. Scite does a nice job, even folding comments, but not for text. Most likely other programmers editors do allow/support that.