Photos is both an image management tool, and an image editor. It imports the images in to a database, lets you organise them, add data to them (such as keywords) and also lets you edit them.
Some others (EG Luminar) are set to do the same job. The library management functions of Luminar for example cannot be used interchangeably with photos - each app is unable to "see into" the others library.
Other apps without library functionality, expect to see the images as individual files in a folder (Eg in the pictures folder and subfolders). Again they are unable to "see into" Photos library.
Your options are:
1 - Export your images from photos to a folder, and then edit them with external apps. The problem with this approach is you will never see the edited file in photos, unless you re-import it, and then you will have two copies of the image in photos. One the original, and the other the version edited externally.
2 - Some of the apps (Definitely Luminar and Affinity) provide plug-in functionality within photos. If this is set up, you can open the image in Photos for editing, then click on the three dots top right, and select (eg) Luminar 4. Photos then opens the Luminar editor inside the photos editor, and lets you use all the Luminar functionality to edit the image. When you have finished, you click (in the Luminar plugin) Save Changes - and the edited image is returned back to photos as the edited version of your image.
2 is how I use Luminar in photos.
The only down side, is photos gets only a complete edited file back. There is no way for photos to store the luminar (or any other app) edit history. You can send that image back to Luminar a second time for further editign, but it would not be possible to change the edits done previously in luminar as it would if you had used luminar stand alone.
You can however still "revert back to original" in photos which will undo all edits to an image, whether done in photos or a plugin - if you decide you want to start again.
