You can achieve what i think you mean as follows:
1. perform one of your saved finds
2. then immediately go in to edit your script
3. select a fresh Perform Find step—by default, FM will present you with the last Find it performed
4. you can now lock that in as the saved find for that script step
5. don't start with a Perform Find step you already have in the script, as then the default will be whatever is already in there—the key is to go straight from the Find you just performed, to a fresh Perform Find script step
Note: you can't, from inside the script editor, select a saved find—these are separate animals—but if you do it as above you can achieve the same purpose. By following these steps you can run each of your saved finds and then lock each of them into its own Perform Find script step, which you can then call as required.
This method did not work. As soon as I performed another saved find for something else, I ran the other script and if presented me with the last one I jut performed. How do we LOCK it in? You save the script but it's not working.