Big news today for Win / Mac / Online versions of Excel. A new Advanced Formula Editor will make LAMBDA and LET far easier. Among the highlights:
New Advanced Formula Editor (Windows, Mac, Online)
Share Lambda through GitHub
Better Recursion Limits (16x larger!)
Formula AutoComplete

Read Chris Gross article:
https://techcommunity.microsoft.com/t5/excel-blog/announcing-lambdas-to-production-and-advanced-formula/ba-p/3073293

Try downloading Lambda from Gist.GitHub
https://gist.github.com/chgrossMSFT/d172fd552cf6893bcdc7942223cb0e55