Hello @GC-James!
To migrate from legacy ${variable} parameters to the new SQL parameter style in Databricks, replace ${variable} with :variable and define those parameters in the UI's "Parameters" section.
Your updated code will look like:
CREATE OR REPLACE TABLE IDENTIFIER(
:environment_name || '.' || :schema_name || '.' || 'cmip6_max_rainfall_' || :run_version
) AS
SELECT *
FROM read_files(
'/Volumes/' || :environment_name || '/' || :schema_name || '/pluvial_flood/scratch/gfes_parquets_' || :run_version || '/'
)