Your Logitech UE Boombox can have eight devices paired with it, and you can connect to three at a time. This lets you quickly switch to one of the other two devices to play audio without having to go through the connection process again. Here's how:
Connect the first paired device to your speaker by selecting it from the device's Bluetooth menu.
NOTE: If you haven't paired any devices, see answer 360023411393 for help.
Connect a second device to your speaker the same way you did in Step #1, and then a third if desired.
NOTE: If you haven't paired another device, see answer 360023411393 for help.
Once you have at least two devices connected, you can start playing audio from one of them.
To switch and play audio from another connected device, pause the current one. Then, start playing the other.