Hello.

Is it possible to add browser plug-in sources to GitHub to translate the interface and website texts into local languages?

Good idea! But i had already asked for it 3 months ago
Sorry, but why didn't you reply to my post instead of creating a new topic to request the same stuff
https://www.freedownloadmanager.org/board/viewtopic.php?f=2&t=18481

Indeed - your entry was the first. But the topic was not very clearly described, so I missed it.

I can think of two things that might get you close to what you want.

There used to be an extension that gave the firefox style download dropdown box. It has since been removed from the store but last I checked sideloading it still worked. Your Download Box

But that's just a drop down not a full seperate window.

I think the only way to get a full external window is to use an actual external download manager, i'm pretty sure Free download manager can do this.