[excel] Are there such things as variables within an Excel formula?

Now you can use the function LET to declare variables within Excel formulas. This function is available since Jun 2020 for Microsoft 365 users.

Given your example, the formula will be:

=LET(MyFunc,VLOOKUP(A1,B:B,1,0), IF(MyFunc > 10, MyFunc - 10, MyFunc ) )

The 1st argument is the variable name and the 2nd argument is the function or range. You can add more pairs of arguments variable, function/range.

After adding the variables, the last argument will be your formula of interest -- calling the variables you just created.

For more information, please access the Microsoft webpage here.