Hi @Manzi, John,
Thanks for reaching out to the Microsoft Q & A Forum.
Please try these troubleshooting steps to fix the parameter pane issue:
Check the View menu: Go to the top ribbon -> select view -> ensure Parameters is checked. If it's unchecked, the pane will remain hidden. Turning it back on should make the parameters pane reappear.
Reset the window layout: sometimes, the pane might be off-screen or minimized. If possible, try to check any minimized parameter pane and try to expand it.
In the Report Data Pane, expand the Parameters node. Recheck if the parameter is correctly configured. If there are no parameters defined, create on manually by right-clicking Parameters -> Add Parameter. Once added, the pane should automatically appear in Design View.
If none of the above works, reinstalling or repairing the installation can reset the corrupted UI settings.
I hope this information helps. Please do let us know if you have any further queries.
Thank you