Tap the post and while holding, drag, and drop it. ⠀
To quickly swap two files, double-click on one, and then tap a file that you want to swap. ⠀
To move multiple posts, double-click on posts, then tap between posts which you want to move. ⠀
To quickly replace the cover for multiple posts at one click: Select multiple posts → Tap ‹Replace› → Select the files from Gallery, which you want to replace with existing files.