Ok, I just tested it, you actually can start a render queue in play mode. Create a new bluerpint, select Editor Utility Actor as base and drop it in your level. Now you can use all MovieRenderPipeline functions such as “Render Queue with executor” to start your rendering. Of course you need to first enqueue something. This however will take over your game and render so it will probably not be helpful in your use case. It is also completely independent of what is happening in game.