You can try this
You can also search the database design report for them. But these variables are not specific to any one table so this statement:
How can you find what local ($) and global ($$) script variables you have created over multiple tables
Makes no sense. Variables are created by the Set Variable Script step or by the Let Function inside a calculation. That last option can create variables anywhere you can open the Specify Calculation dialog so a DDR search is your best bet short of using a third party tool such as Base Elements to search the DDR for you.