Thank you for letting me know how access to BSP tool in UE5. Also, it is good to know that UE5 will remove BSP in the future. I watched the video mentioned here then activated the Mesh Editing Tool and started learning it to be ready for future update.
My favorite workflow was to do gray-boxing with BSP then converted them to invisible blocking volumes and place modular static meshes inside the volumes for human eyes. It was useful because placing visible meshes rarely broke a game play in the workflow.
It seems I won’t have to change the workflow thanks to the Mesh Editing Tool, supporting to convert between a mesh and a volume. (UE5 won’t remove a blocking volume, right?)