Ah, when you said "the file names are no longer visible" this sounded like they were visible in the export in previous app version.
How exactly do you want to position images in the exported .html file? You can export to .docx, open the file in Microsoft Word and move the images around there. You can also add text to the file in Microsoft Word.
How exactly do you plan to edit a .html file?
When you say "add text to the images", do you mean add text on top of the images or above/below the images? You can also do that in Microsoft Word. How are you using the file names in Diarium? Are you using them to describe the image, meaning that you edit the file name in Diarium after attaching the file?