I tried to put a share menu into Nitro, but the Share API for Mac is very weird and doesn’t work well. Photos and Preview seem to do special Apple-only things, but perhaps it will get better in the future.
Export presets are on the list.
Does the Qimage plug-in run as a separate app? If so, you can use Export and then specify a post-export action which opens Qimage. If Qimage identifies itself as an app that can view images, then it should show up there.