When I hover a tweet and then hover over the "favorite" star, I see "favorite from ", where username is the first user I logged in with. How can I change that, so I can favorite from a different user I've set up? I've tried changing "set as default" username in settings and it doesn't affect it.
Click on the post you want to favorite, then from the "..." drop down menu in the lower right corner chose "Favorite from accounts".
Note that you have to click on/activate the post first to get this menu option.