WORKAROUND:
There is no way to set global defaults for paramters that are shared by multiple reports. You can however copy the reports you use frequently to the My Reports folder, enter the parameters you want to be used each time the report is run and then click "Save parameters as default" under the Manage Parameters section. Each time the report is opened from the My reports folder, it will have the saved parameters already entered.
Please note, the contents of the My Reports folder is visible only to the user who owns it. If you would like other users to be able to use reports with predefined parameters, you will need to copy the report to the My Reports folder, enter and save the necessary parameters and then copy the report to the Published Reports folder. The contents of the Published Reports folder is visible to all report users. The reports in this folder cannot be modified, but the parameters can be overwritten allowing the report to be run with different settings. Any parameter changes to reports in the Published Reports folder are not saved.
STATUS:
Enhancement request TF00420377 has been submitted to Development for consideration in a future release of Enterprise Reporter