Isn't worth a thing, compared to Thumbnail Zoom Plus.
As Thumbnail doesn't work on the new version of Firefox, I disintalled the latter and came back to the old one I had before.
The only way to have Thumbnail work.
Too many add-ons don't work on the new Firefox version so I threw Imagus directly in the trash, with the new Firefox version.

OMG
WOW
Everything is here.
LOVE IT :D

Wish I could extract the settings though :D

это абсолютно топовое ,очень важное и полезное расширение!
создателю большое уважение.

Edit 31/03/2020

Seems to be working fine for now.

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It's been working perfectly for a long time but now for some reason it has started to work less and less on sites...
I just came from IMDB and it's not working there.

And yes i've updated the sieve.

Soms doet ie het,soms,zomaar,doet ie niet.

Esta extensión es fantástica! Cuando encuentras una imagen que se puede ampliar, pero no guardar directamente, puedes mantener el click derecho sobre la miniatura y la ampliación de mantendrá. Cuando se mantenga, le das de nuevo click derecho y podrás guardarla como siempre.

Works great!