Once the first part of our custom TinyMCE media plugin is implemented (MDL-75258, which adds image functionality), we can introduce media manager functionality, which allows you to manage all media (image/video/audio) content that has been added to the current instance of the editor using the new media plugin.

For this iteration of the TinyMCE integration project, this just requires porting the existing media manager functionality from Atto over to TinyMCE 6. Since Atto simply displays that manager in an iframe, this should just be a matter of finding the relevant place in TinyMCE to add this, and taking the same approach (ie displaying an iframe of the file manager in the same way).

One of the reasons the manager is required, is that when you delete an image within the editor, the file still exists in the draft area, so is carried over when the content is saved. To avoid that, you must go into the media manager, and delete the image. There are possibly ways this could be handled automatically in future, but this is out of scope for the current work.

This may form part of the plugin created in MDL-75258, or will possibly need to be a separate plugin, so deciding that forms part of this issue.

Note: To work on this issue, you will need to create a branch based on both MDL-75071 and  MDL-75258 (assuming this is not worked on before those land in core, which is likely).