You can cancel a running conversion in one of two ways. This depends on the state of the process and the file type.
Once you start a conversion, the "exit" button switches to "cancel" (or the progress dialog opens, with a cancel button). When you click this, the program tries to stop the current operation and remove all temporary files. If this is not possible (for example during a MultiTerm reorganise), the window background (or the border of the progress dialog) turns red. In that case you can either wait until it finishes, or abort the conversion.
If a clean cancel is not possible, click the exit or cancel button a second time, and the application will close. It may leave some temporary files behind, or an incomplete target file. It's safest to delete any output files created by an aborted conversion. They may look usable, but their content is unpredictable.
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