It's normal for a new bookmark to be stored initially in Other Bookmarks. In the little panel that pops up for a few seconds, you should be able to select a different category or a folder. What happens when you try that (or click the star after bookmarking to call the panel back up)?

Also, there is an add-on which can switch the starting folder from Other Bookmarks to a different folder of your choice. See: https://addons.mozilla.org/firefox/addon/default-bookmark-folder/

Thanks jscher2000, that's the problem, except for a single occasion, I have not been able to bookmark a site in anyone of the other 20 some folders I have. As I am writing this reply, I am trying to bookmark this page in other folders with no success, again only in "other bookmarks". I am just coming back to Firefox because you still support Mac OS X Mavericks, but I have used earlier releases of FF since it's inception, but never has this problem come up. If necessary i can save pages to other bookmarks then cut/paste them to other folders, but it ought to work the normal way.

jscher2000, I installed Waterfox 56.1.0, a browser I was using for quite awhile when I was running Mac OSX Mountain Lion because it was supporting 10.8.5, still the same problem, but it is much faster than FF 59.0.2. Also there were many more plug-in's installed which I was used to having, so I am going to stick with Waterfox, have uninstalled FF. Thanks, for your help.