name manager rejecting lambdas

If to take your sample literally and insert xyz from the right as abc manually in Name manager, it works

Hello dror_erez​, 

Excel’s Name Manager isn’t rejecting your LAMBDA because of length or parameter count, it’s rejecting it because of syntax.

Square brackets [ ] are not valid in LAMBDA definitions. You can’t declare optional parameters this way. Every parameter must be listed explicitly. To simulate optional arguments, use the function ISOMITTED() inside your formula.

Example: =LAMBDA(array, slice1, index1, return_index_slice2, index2, return_index, if_not_found, logic, headers, function, LET( idx1, IF(ISOMITTED(index1), 1, index1), idx2, IF(ISOMITTED(index2), 1, index2), ... ) )

Excel allows up to 253 parameters in a LAMBDA, so your 8–10 arguments are fine. The key is that they must all be explicitly defined. If your formula is very long, consider breaking it into smaller helper LAMBDAs and referencing them. This makes debugging easier and avoids Name Manager hiccups.

Remove the square brackets and handle optional arguments with ISOMITTED() inside LET. That will allow your LAMBDA to be saved in Name Manager.

Extra Tips for Complex LAMBDAs:

• Modularize: Create smaller helper LAMBDAs for repeated logic and call them from your main function.
• Document parameters: Keep a separate sheet or notes to track what each parameter does.
• Test incrementally: Build and test your LAMBDA in stages before pasting into Name Manager.
• Use descriptive names: Clear parameter names make debugging much easier later.
  
  

  Microsoft Documentation:
  LAMBDA function: https://learn.microsoft.com/en-us/office/troubleshoot/excel/lambda-function
  Use custom functions as LAMBDA parameters: https://learn.microsoft.com/en-us/office/dev/add-ins/excel/custom-functions-lambdas.  
  ISOMITTED function: https://learn.microsoft.com/en-us/office/troubleshoot/excel/isomitted-function

What is LET(...) here? May be issue with LET functions parameters. Below formula works fine with name manager. For a simple calculation I have just used SUM() inside LET() function.

=LAMBDA(array,slice1,[index1],[return_index_slice2],[index2],[return_index],[if_not_found],[logic],[headers],[function],LET(x,array,y,slice1,SUM(x,y)))