CHILDREFS is only available in Spreadsheets.

• Formula help will not suggest CHILDREFS when creating formulas in embedded tables.
• Formulas containing the CHILDREFS function will evaluate to 0 if pasted into an embedded table.
  • This is because there are no child sheets to an embedded table.
  • This behavior matches how cross-sheet formulas work in embedded tables today.

Formulas containing CHILDREFS export as-displayed. 

Formulas supporting CHILDREFS:

• AND
• OR
• COUNT
• COUNTA
• COUNTBLANK
• SUM
• PRODUCT
• CONCATENATE
• AVERAGE
• AVERAGEA
• MAX
• MAXA
• MIN
• MINA
• MEDIAN
• STDEV
• STDEVA
• STDEV.P
• STDEVPA
• STDEV.S
• NPV (for all arguments other than 1)
• TEXTJOIN (for all arguments other than 2)
• RANK (for argument 2)
• RANK.EQ (for argument 2)
• RANK.AVG (for argument 2)
• SMALL (for argument 1)
• LARGE (for argument 1)
• IF (for arguments 2 and 3)
• IFS (for the even arguments 2, 4, 6, …)
• CHOOSE (for all arguments other than 1)