I have Mozilla set as my default browser to save my previous session. When I wanted to view two web pages in two windows, I dragged a tab out of Mozilla to create a separate window. Later, when I closed my session, I closed my regular browser with the tabs I wanted to recover, including the separate tab I was using as a reference. To my surprise, when I turned on Mozilla later, it only saved the last separate tab as my last session. Is there any way to recover the previous session?

Found it: https://support.mozilla.org/es/questions/1340206#question-reply

Hola Entiendo que encontraste la solución en ese caso solo restaría que marques la consulta como solucionada (eligiendo la respuesta de la solución) para que sirva a otros usuarios. Gracias