[x] this does not actually perform the save function after the button is pressed, it just logs the user in; instead, this should perform the 'save as...' function after logging in
[x] Can be separate ticket if you wish: As a logged-in user opening a scene which is not owned by me (I am not the author) should also show Remix button with "save as..." function
Great start @rostyslavvnahornyi !
To merge: