Modify, add or remove one or more file(s) in a repository.
Open Workbench on that repository and switch to Commit view.
In the file list, right-click one of the files and select "Detect renames..."
In the dialog that appears, click the "Find Renames" button.
All of the the dialog controls become disabled, and there is no way to exit the dialog (not with Close button, Ctrl+C, or Esc) until all potential files have been examined.
This is particularly painful in large repos and/or if the "Only consider deleted files" checkbox is deselected.
Suggested fix: leave the "Find Renames" button enabled, but change its text to "Cancel" after it is pressed. When it is pressed while the "detect" operation is in progress, it should abort the operation, re-enable all controls and set button text back to "Find Renames".