You can let any recipient decides who signs next.
It can be used for any recipient, including yourself.
The 'decide later' button is often used for witnessing; you'd normally expect a signer to nominate their own witness.
But it's also usefully combined with an approver role. Add yourself as an approver before the unknown signer, and let that approver role 'decide later'. You will get notified when the document is at the relevant stage, and then decide then who will sign it.
On the send page simply click the 'return icon' just to the right of the relevant participant's email input.