Filemaker is a database, and operates on a different data structure than an excel spreadsheet.
Thus the rules for Undo and Redo are different as well, since in excel you are working in a single instance of a single file, and in filemaker you are working in a record instance out of many possible records in a file.
This article from filemaker explains how data is committed (saved) to the database.
As long as you don't commit your data, you can undo and redo.
If you want to force manual committing of data, this article explains that: