In grid tied inverters with batteries the transfer switch can be built in to the inverter or it can be an external switch that the inverter talks to. Similar to how you would use one with a generator setup.

And indeed these are uncommon, mostly because they tend to be more serious devices. Victron and formerly Xantrex make nice ones, but the inverter alone probably costs more than a complete balcony solar installation.

For the solar balcony and more common rooftop solar setups there is only a simple disconnect, but both a transfer switch and a disconnect are the same thing: a (usually beefy) relay, but the transfer switch variety switches your house between the inverter and the grid whereas the disconnect just physically disconnects the inverters output. The downside of that setup is that if there is no grid but you do have solar that you still have no power.

Most of these wouldn't be able to power anything but the smallest installations anyway (300 W or so, typically), and don't have a battery to store any excess (as if there would be any...).

As soon as you add a battery it makes good sense to use the transfer switch: you can disconnect from the grid but the inverter can keep running to power your house and if you're lucky the solar will replenish it fast enough during the day that you can hold over for a while.

The big rooftop inverter that I have has a built in transfer switch but I'm not using it right now simply because I don't have a good way to route the wiring to and from the inverter. It is stuck in my garage with the main distribution panel on the other side of the house. In my old house in Canada that was all designed from scratch and there we had the house entirely off-grid with the transfer switch hooked to a genset if the power was out for longer than the battery could sustain us (48 KWh so that usually was good for a couple of days).