Hi Mark F!
Thank you for writing to the Microsoft Answer Community Forum, I am Shakiru, an independent advisor and a user like you, and I am glad to be helping you out today.
I'm sorry, Excel do you have the capability features for Alt + X to change the symbol for code like Microsoft Word.
However, you can suggest the Microsoft developer via the feedback portal here: https://feedbackportal.microsoft.com/
You can also click on Help in the Microsoft Excel spreadsheet> Select Feedback > Select I like something and enter the information you would like to suggest. Thank you for this.
Kind Regards, Shakiru