A Detail Library is a good thing to have, and it is never too late to develop one. The advantages of a Detail Library are:
If the lookup and retrieval processes for your Detail Library are off-putting, or if they rarely result in helpful info, then your system won’t be used and lots of effort setting it up will go to waste.
So the main issue is how to catalog the contents of your library to describe what is on file and to guide you in retrieving what you select. That issue was solved over a century ago by Melvil Dewey. A customized version of the Dewey Decimal System is just the thing you need. The best system out there for this purpose is UNIFORMAT II. UNIFORMAT provides the overall framework for storing and retrieving re-usable detail files. At the same time, like the Dewey Decimal System, new additions are easily incorporated into the system.
Now that we know how organization will work, start clipping details in whatever convenient format works best - JPEG (e.g. phone camera), PDF (scans), HTML (web pages), DWG; and txt or doc to record instructions and experience. Even an audio file can be saved. Give each of them a name in the format: Uniformat ID - detail number* - descriptive name; i.e. A2020-A-Masonry Basement Wall. Let the file extension convey information about content or add a word or two to the “descriptive name”. Use the files to store information that will help the next user; and consider a procedure that logs which projects used the detail and anything new that is learned.
Store all of this in the cloud, e.g. an Evernote notebook, or a Dropbox folder (both support sorting by name, which is crucial), where you can easily add to and retrieve from anywhere. Dropbox has the advantage of being free and allowing sharing of the Detail Library folder with everyone on the team. The advantage of Evernote, although the keeper of the Detail Library notebook will need a Pro Account ($50/yr), is that it is simpler to add information to the one note - additional comments, photos, files or even audio files.
Concentrate on gathering useful information; then, as you use it, create, clip and store the CAD file in the same folder in Dropbox using the same name for the CAD file; or add it to the note in Evernote. Having a usable CAD detail is the holy grail of the Detail Library, but having a ready solution to a condition is a major help on its own no matter what format.
Architekwiki has about 50 details so far and plans to add many more. Take advantage of these to start your Detail Library.
* If you think it is likely that you will have more than 26 details in each group, then use 00, 01, 02, 03 etc as the detail number to accommodate 100 details in each group. There isn’t any point in storing unique details. Go for archetypal. Also bear in mind that UNIFORMAT II has additional levels, whose numbers you could implement. This (link) reference sheds light on the system.