There are 2 options
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make use of whatever features there are available on the platform that you are hosting the repo to start the workflow via the API rather than the default webhook interface. Via the API you can provide values for the defined parameters.
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read up on the Dynamic Configuration feature of CircleCI. This basically allows you to have one config.yml script file that is able to then call another one. This allows the first script to pull together all the dynamic info needed and then pass it to the second script as ‘static’ values. The starting points for this feature are