Brasero multiple disks

[SternData]

Brasero seems to have a feature to let one burn multiple disks when the
content is to large to fit on one.

I selected about 40 MP3 files for an audio CD.  Brasero correctly notes
that that's too much for one CD.  A button appears that says "Burn
Several Disks".  Sounds good. But, when I click it, there's no BURN
button.  How do you actually get it to burn several disks?