If you're talking about the dog face itself, then you just have to change "minimum image width" option, the default value is 256px so it ignores anything smaller than that, while the picture you linked is 160x160.
Or you can just hold Shift while hovering your mouse over that picture, it ignores the size completely that way.

Thanks for the feedback. You can bind another hotkey you like in the options.

Could you please check if the button appears on any of these:
https://upload.wikimedia.org/wikipedia/commons/8/87/Schlossbergbahn.webm
https://upload.wikimedia.org/wikipedia/commons/3/39/Lichtenstein_img_processing_test.png

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I know I'm telling this every time, but try deleting and installing this extension again.
I'm gonna make proper settings reset/import/export functions in next update, so it probably would be much easier to debug problems like this one. But for now reinstalling would be the fastest solution.

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Never thought someone uses this mode, as it said, it's experimental. Thanks for letting me know, will try to fix this option soon.

"уже сохранённые делает приглушённым цветом"
Это можно. Под опцию. Сорт оф. Бегать по всей странице и перекрашивать все картинки я точно не буду, а вот под курсором чтобы картинка или даже сама кнопка как-то окрашивалась, если уже сохранялась, это можно сделать.

Maybe I messed up with how these folders are saved in settings, had to redo it few times.
The easiest would probably be to completely uninstall the extension, so it would delete all settings, and then installing it again. Or try "Reset all" button, maybe even that would be enough.
I'll re-check everything, maybe missed some bug. Thanks for the feedback.

I'd like to do that, but it's impossible with current Downloads API. I can't save files to any folder outside of your default save folder, and I can't open "Save As" dialog in your last saved folder because it might be outside of it as well.
And even IF we're talking only about the folders inside the default save path, which there's no way of knowing, it would only be possible with some really dirty hacks.

https://bugzilla.mozilla.org/show_bug.cgi?id=1342563
They're talking about possible "useLastDir" option, that's exactly what you want. I'll add this feature the moment Mozilla implement it.
Thanks for the feedback.

Really sorry about that, just uploaded the new version, it should work again. Thanks for letting me know.

Thanks.
That's how it works now. Firefox Extensions don't have access to your local files. If you saved the file recently, I can be sure if it's a duplicate, but for your old files, the most I can say is if the file with this filename already existed, which is not enough, because some pages might have different pictures with the same filename, something like "image.jpg". Or some "1.jpg" file would prevent you from downloading another completely different file with this name.

It still happens sometimes. Please give me an example and I'll try to fix it.

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Thanks for the link, I'll fix that in the next version.

>standard dialog for saving the image
Sure, no problem. In next version.

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added in 0.4.9

Thanks.