A major missing feature for playwrights and screenwriters seems to be the ability to properly format dialogue that's spoken at the same time. To adhere to standard script formatting, such dialogue should appear side-by-side, but Scrivener doesn't offer this.
1. In US Stage Play compile, make sure "Convert Preserve Formatting blocks to dual dialogue tables" is selected.
Dual Dialogue.jpg (79.99 KiB) Viewed 530 times
2. To adjust the character name spacing (which seems to be corrupt in the template), choose Format > Scriptwriting > Script Settings > and then tweak the line indents to suit (I went from 3 to 2 inches in this project – probably different for US paper sizes).
From the sample given in the manual – where Lorenzo, Jemma, and Felicita are all aligned – I assume this is just the way it works: only Guido gets shunted over to a separate column, implying that the core alignment is universal and that dual dialogue shifts the second speaker over in isolation (can probably be changed in secondary software if compiled to an editable format).
Can't see a way to change this, but perhaps someone else can.