The work of the last year is ready. 
The upload of files in the backend got revisited and re-coded
* It is now possible to upload files with drag and drop.
* You may turn or flip the image afterwards
A matching documentation will follow within the next weeks on
1. Select an existing gallery
2. Drag and drop a batch of files into the drag area (tried more the 40 at once)
These will be uploaded and assigned to the gallery which needs time.
3. If you want to annotate text or change the titles then you can press button "Add image properties"
   A window with all actually uploaded images will appear where you can change the title and description
   The images can be turned or flipped there also.