Ive thrown together a simplified example :

Save Case code:
Set(CaseID, Patch(
'[dbo].[CASETABLE]', Defaults('[dbo].[CASETABLE]'),
{
CaseName: CaseName.Text
,CaseType:CaseType.Type
}).ID)
; ForAll(Issues, Patch('[dbo].[ISSUESTABLE]', Defaults('[dbo].[ISSUESTABLE]'),
{Case: CaseID
,Name: ThisRecord.IssueName
,Type: ThisRecord.IssueType})
; ForAll(Evidence, Patch('[dbo].[EVIDENCETABLE]', Defaults('[dbo].[EVIDENCETABLE]'),
{Issue: <IssueID>,
Name: ThisRecord.EvidenceName
Type: ThieRecord.EvidenceType})
Its how I feed the IssueID generated on the save of an issue into the evidence I cant figure out.