Unfortunately that’s the limit and the only two ways I know to get around it is

1. Create a database package with your code and just call functions/procedures

2. Start cutting characters, i.e. remove comments, remove indentation, cut down names of params etc.
3.  

As anmise has mentioned, the best way to do this without having to write unreadable code with variable names that don’t make sense and such is to create a utility database package and write a method that you can call inside the PL/SQL block of the menu item. 

Or you can write pieces of the code in a event action and Call the event code with the custom menu.