The trial version and registered version of Filmora for Mac is functionally the same product. The limitation is that there will be a watermark on the exported videos. You need the registered version to output files without watermark.
So to remove the watermark, you need to ensure that you have managed to register the program. Secondly please select Open Project/Open Recent from the top menu to reload the project file (.WSVE file). Lastly press Export button to export the project file again, there will be no watermark added any more.
Note: After you purchase and register the product, the output video with watermark cannot be removed, and you need to output the file by using the registered version again to get the output files without watermark.