Trying to add User Defined Function to the personal workbook

As a late adopter still using Excel 2007, I prefer to put UDFs that I intend to use in worksheet formulas in any sheet into an add-in file. From an add-in, I can call them just like any built in function =MYUDF(arguments) or =25*MYUDF(arguments). I learned early on that, if I store a UDF in a file like Personal.xlsx, then I need to preface the function call with the workbook name =Personal.xlsx!MYUDF(arguments) [I think that would be the right syntax -- haven't done it that way in a long time]. This describes the process of creating an add-in in 2016 (basically the same as it has been since at least 2002: https://www.dummies.com/software/mic...k-file-in-vba/ ). Once created, you can add the add-in to Excel using the File -> Add-ins -> Manage add-ins dialog: https://support.microsoft.com/en-us/...8-403625a0b460

I see indications that MSFT is trying to move away from VBA and these old style add-ins. If you are a forward looking type that wants to develop UDFs that will be usable in future versions of Excel without relying on MSFT maintaining support for "legacy" approaches, it might be worth looking into the new development/extension/add-in models and whether they are compatible with your 2016 version or not and so on.