OCs is there a way now in 0.14.0 to limit the available layouts (for desktops as well as for mobiles, thus the CSS-only solution of Jan 13, 2023 would not be sufficient)?
I can't see that anything changed since the CSS solution, which should still apply. I guess this should perhaps be a Javascript config option though, I will add it in next release. As for "desktops as well as mobiles", the solution would apply regardless of device. If you want to show/hide layout buttons per screen size, you could use CSS media queries.
OCs I have found images (at least JPGs and PNGs) actually work properly without a suffix — they are recognised and shown properly. Is that a feature one can rely on in future releases? The goal is to show image titles in the gallery without suffixes (this, at least for me, nicely removes the need of custom titles, debated in other threads, and potentially problematic).
Yes, because if the file has no extension, PHP will attempt to get "mime type" from reading the file, and we will then know it's an image/jpeg. This outcome should be future-proof, although using this method to specifically create titles by excluding the extension in the filename, is still a "workaround" for your specific usage.
OCs The logo goes to a separate row even though there's ample space below:
Well, it's not like we measure the exact logo width and available space between the buttons, and then place it there. There might be additional buttons like login, update, settings, select-mode etc, and the logo could easily be much wider than yours. Besides, in your screenshot, you can generally see mobile/tablet-vertical mode, in which case it's entirely fine that there is an additional topbar with the logo on top where it's nice and centered ... If you keep it "in the middle of the available area" in the section below, it's not even centered.
We use breakpoints to simply decide the logo placement, and currently is the sensible and subjectively best choice.
OCs with the footer it does not seem to be possible to scroll up enough so that it does not obscure the bottom parts of the images:
This is footer_fixed or footer? I provide these options as complimentary ways to insert your own HTML. Files Gallery is not a "website" that you can design with custom elements however you like. Space is extremely limited. In your screenshot, it looks like you have the fixed_footer on two lines ... We don't programmatically add additional margins by javascript calculated from the height of your footer. You use this at your own discretion, and customize via CSS if must be. If it can't be done with custom.css, then how am I supposed to provide this functionality up front?
You can use the footer and fixed_footer to add basic text into the footer. If need be, you can customize by CSS. I can't include any additional magic functionality beyond that unfortunately. My normal recommendation would be to not use it at all. It's OPTIONAL, or use at own discretion, as long as you know how it affects the interface.
As stated in the logo / custom html docs:
Default styling on custom elements is limited. If you want to modify or adjust CSS styles, please use custom.css. Keep in mind, CSS adjustments may impact the interface, which has limited space.
OCs I've noticed a typo in the current Czech translation: layout should be “Rozvržení”, not Ror
I think it should be like this:
_c.config = {
// custom language options
lang: {
// override or create new languages
langs: {
cs: {
layout: 'Rozvržení',
},
}
},
}
As far as I can see, "layout" is already "Rozvržení" In Czech.

OCs Is there a way to set up a different logo picture based on whether the bar where the logo is drawn has a white or dark background?
Best and easiest would be to use a semi-transparent logo that can be used on both dark and light backgrounds.
If you need to modify the logo based on theme, you would need to use header and topbar options to insert your own html, and then use CSS backgrund-image to display your logo with the source depending on the current theme. It's not possible to do directly with the logo option.
You could create a custom javascript solution that injects different img source depending on theme, and changes it when then theme changes, but this is very clumsy.