Is it possible to create a folder on a smart phone?

Yes. You can create folders and work with files in Android. However, it sounds like what you want is something like Pocket. If you are viewing a link on Facebook that you like and think you may want to revisit some day, you can save it directly to Pocket. Then you can browse or search your saved content in Pocket later on.

I may have misunderstood, however. Maybe you could describe exactly what you are saving in folders on your desktop. Photos? html files?

FB pages, like videos of the grandkids that my kids post.

The other day a guy shared a post so he could “find it later.” I said, “Make a folder!” He said he can’t because he’s using his phone.

Well, I think Pocket would work for most of it. And I suppose it depends on how the videos are shared. If they’re uploaded directly to Facebook, you click “Save this video” in the Android version of Facebook, which apparently will “Add this to your Saved Videos”. But if you are talking about youtube videos, you can save them to Pocket, Dropbox, or any other service.

I use an app called Files Pro for documents.

You can. I found it painful to do on my Samsung phone. That might just be me though! I did a few google searches to find out how.