So far none of these responses really answer the original question. I have been looking for something similar too - a "smart" transfer switch that lets you programmatically or manually remotely switch individual circuits between grid and generator (solar). It looks like there is a potential solution with products like the generac smart transfer switches with additional modules added to them, but I haven't looked at them too closely because they are way more money than I would want to spend on a transfer switch.
As was mentioned above, most of the AIO units support switching between grid pass through and running on the inverter. I think I'm just going to settle on a manual Reliance Pro Tran 2 transfer switch that has 10 circuits with individual switches to switch them individually between grid and solar inverter power. You still have to go and physically flip those switches if you want to change a circuit, but I don't think one would end up changing them very often anyway. Still - it would be nice to have an option for one like the EcoFlow Smart Home Panel that would allow you to do it remotely. Even better would be one you could tie to an automation solution like home assistant or something to automatically switch them with some intelligent programming. I've spent a good amount of time looking for such a thing that doesn't cost in the thousands of dollars, but so far no luck.