I'm a photographer and I often upload private galleries for clients with a password so that they can go through a photoshoot and select individual images for retouching, so being able to see the file name as an image title is really important.
I used to use the following code in the individual galleries 'Cog icon'>advanced>code injection box;
Which I got from another user.
I'd then select 'show title' in the galleries settings, refresh the page and voila. But I havent done this in a while and since Squarespace have updated the interface to do this I can no longer find 'show