When were bookmark-like "flags" introduced in America? (Certainly prior to 1908, based on this reference.)

I've done something like this when I think a particular reference(s) can answer a question related to a train of thought. But I keep cards of unread sources at the front of my sources section so that it's easier to pull it out frequently to prioritize and decide what I should be reading or working on next. These will then have links to the open questions I've noted, so that I can go back to those sections either as I'm reading/writing or to add those ideas into the appropriate folgezettel. These sorts of small amounts of work documented briefly can add up quickly over time. Source cards with indications of multiple open questions that might be answered is sometimes a good measure of desire to read, though other factors can also be at play.

That to-read pile of bibliographic source notes (a mini antilibrary) is akin to walking into a party and surveying a room. I may be aware of some of the people I haven't met yet and the conversations we might have, but if there are interesting questions I know I want to ask of specific ones or conversations I already know I want to have, it can be more productive to visit those first.

This sort of practice has been particularly helpful for times when I want to double check someone's sources or an original context, but don't have the time to do it immediately, don't want to break another extended train of thought, have to wait on materials, or may have to make a trip to consult physical materials that are singular or rare. For quick consultative reading, this can be a boon when I know I don't want or need to read an entire work, but skimming a chapter or a few pages for a close reading of a particular passage. I'll often keep a pile of these sorts of sources at hand so that I can make a short trip to a library, pick them up, find what I need and move on without having to recreate large portions of context to get the thing done because I've already laid most of the groundwork.

It used to reside here: http://booktwo.org/openbookmarks/about/ but isn't active anymore.

A newer incarnation is here: http://booktwo.org/notebook/open-bookmarks-the-beginning/ but it too appears to be dead

<small><cite class='h-cite via'>ᔥ <span class='p-author h-card'>Sam Anderson</span> in ‘What I Really Want Is Someone Rolling Around in the Text’ - The New York Times (<time class='dt-published'>06/09/2021 12:13:02</time>)</cite></small>