Fig.: in a position of low priority, said of something of a secondary importance or priority. The concept of the idiom is that the pot on the back burner is not your primary focus, but you're keeping it aliv

For awful as it may sounds, we have to acknowledge that, because of the congestion in the hospitals due to the pandemic, many "normal" cases took a back burner for quite a long time

Per quanto brutto sia ammetterlo, bisogna riconoscere che a causa dell'intasamento degli ospedali, a seguito della pandemia, molti casi "normali" sono passati a lungo in secondo piano

She will have to put her career on the back burner for a while so that she can take care of her triplets

Per un po' dovrà mettere nel cassetto il pensiero della carriera per prendersi cura dei suoi tre gemellini

This expression comes from cooking. A standard stove has four burners, two in front and two in back. A cook usually puts food requiring less attention, like simmering or heating, on the back burners, while the front ones are used for cooking needing more attention