Browse Server Button on Link Dialog in Ckeditor so a list of files on the site can be displayed

In Drupal 7, with ckeditor installed, the link dialog has a Browse Server button that allows the user (with the appropriate role) find a file already uploaded on the server : Backdrop moved ckeditor into the core but this functionality is missing: Link autocomplete doesn't work for two reasons 1) if my clients knew the exact (or close) file name and structure, they would just paste it and 2) the autocomplete never finds the file. At most it brings up 3 things, all of which are pages or taxonomy, none of which are files. No matter how I type the begining of the file name (and I have tried a number of different ways of typing it in).

The end result is that the clients are just uploading files multiple times even if it's already on the server. It's rapidly becoming a space problem in a few days. I'm going to provide them a workaround process, but it is only a short term answer because it requires them to go to their user page, find the file in the file browser and literally go back to the page and past the URL in. This is not a long term workable solution.

The browse server button exists in the insert image dialog in Backdrop.

The site has over a thousand pages and thousands files. Some of them should be deleted, but they are not and that's not my decision - that's the clients. They will clean up where and when they can, but will still have easily over a thousand current files and probably at least 500 - 1000 pages. This isn't a huge site either. It's one of our bigger client, but not the biggest and we have easily 10 other clients that will have the same exact problem. I will lose the clients if I don't find a better solution.

Ckeditor in Drupal 7 uses either CKfinder (the default) or IMCE, or other 3rd party image browser. If you don't have anything else, by default it uses CKFinder. I don't really care if IMCE is used, although I do have it installed. I also don't care if this is done as a contrib module or included in core, but I do need a solution or guidance on a solution as soon as possible. This is a live site and will be the production site for the client in 1 day.