How to select platforms for add-on

Is there any difference in desktop platforms for add-on if I distribute on AMO? I submitted my first addon and selected only Windows platform. Can I select Linux and Mac Os X?

The best is always to just select all of them. It is unlikely it won’t work on another platform – if it would, you would likely know about it.

Yes, I found only 2 differencies for firefox extensions in desktop platforms - messages to native apps and browser style files. But I didn’t use it in my add-on. Now I want to add other desktop platforms and can’t find option to do it. Should I upload new version to add platforms?

In the Developer Hub, you can go to Status & Versions, click on the version you want to modify, and then look for the platform information to change it.