This is related to Defensive Workflow Design Part 3 - Separation of Concerns to have a workflow to be less than 500 KB.
My assumption here is that each time you add a Workflow Action, a certain file size is added to ‘*.nwf’ file.
You can check the corresponding file size of each Workflow Action by:
In this case, workflow action "Log in history list" will be 17.4 KB in file size.
So another question will be, Is there a table out there that list all Workflow Actions and their corresponding file sizes?
If there's a table out there, you can use it for the following: