The current "sort by date" option sorts the images by EXIF/metadata creation date *AND*, if metadata are not available, by the 'last modified' information of the file system. This is a wise way for the most of us. But there are users like me who just want to sort by plain file system modification date because they have files from a variety of sources in one folder and the metadata date is irrelevant.
Example: Someone is a collector of photos from Tumblr. The file names are cryptic numbers and don't say anything. She just wants to display the folder in Gwenview like she could view it with Dolphin's "sort by date": The last *ADDED* pictures are *ALWAYS* at the end. (Forget these strange servers that give your downloaded file the real upload date on the server filesystem for this scenario; Gwenview cannot do anything about them.)

I would be very glad if you developers could implement a second 'sort by date' option.
BTW: I like Gwenview very much, it is a extremely great image viewer and I'm amazed with each KDE SC what you did to further improve the experience. Thank you! :)

Reproducible: Always