Hey @Dink0, thanks for posting and welcome to the Bose Community.
I hope you are enjoying your new Bose Sports Earbuds! 😁
As mentioned by @Hector_B & @Sam_F, I'd like to reiterate:
We do not recommend just using the left earbud. If you'd like to just use one earbud, the right would be the best. This is because when you pair your Sports Earbuds to your phone, tablet or laptop, the Bluetooth connection occurs between the source device and the right earbud. The signal is then beamed over to the left earbud. So if you were to take out the right earbud and place it on a table, that earbud would go to sleep in about 20 minutes and, when that happens, the left earbud would lose its Bluetooth connection. Similarly, if you were to place the right earbud in the charging case and close the lid, the left earbud would lose its connection immediately.
As for calls, it’s worth noting that the microphone system that picks up your voice is located in the right earbud—another good reason to opt for the right earbud when you feel like only wearing one.
Just be aware, when you choose to listen to the right earbud only, you won’t be able to access the touch controls on your left earbud.
I don't have any information regarding the ability to switch which earbud allows which controls, but I'll be sure to pass along your request to our development team.
Let us know if you have any further questions.