I am using this search engine from Deeple from Japan.
However, when I type Japanese in the prosecution box and select "Deeple" to jump, Deeple's auto-determination is inevitably in English.
If I type English in the search box, it is interpreted as English.

Unfortunately, it defaults to "English to Spanish" translation for a while now. It used to default to "Auto to last used target".

But it is the only DeepL Translate Search Plugin I found that replaces "+"s with spaces in the search query.

The plugin configuration does not allow to define target language. Based on my IP it choose wrong language... I am not sure if possible, but i would welcome if it adds the search shortcut @t , meaning i type "t word" into address bar and it would use deepl to translate word.

UPDATE: other extension works to detect the language and set destination language per my choice: https://addons.mozilla.org/en-US/firefox/addon/to-deepl/
source: https://github.com/rewkha/firefox-to-deepl/releases