Hello! Thank you for reaching out! I can see how controlling each individual TV at a time will be useful. Unfortunately, the way our TVs and remotes are set up you are unable to do this the way you described. You can however try this to control at least one TV at a time but may require using all three remotes.
First I would recommend resetting all remotes by taking the batteries out and holding down the power button for at least 10 seconds. Then point the Smart Remote at the remote control sensor on the TV. On most Samsung TVs, the remote control sensor is located on the lower right-hand side of the TV. If not, it is directly in the bottom center. Make sure to try and cover the sensors of the other TVs if they are super close to avoid them getting paired to them or unplugging the other TVs.
Next, press and hold the Return and Play/Pause buttons simultaneously for at least 3 seconds. Your TV will begin syncing with the Smart Remote. Then a message will appear, indicating that the remote is now connected to your TV. Do this with each remote for each TV.
Now I cant 100% guarantee this will work as I do not have this kind of set up to test it on. This will also depend on if you have the smart remote or not. But if this does not work then there would not be a Samsung way to get this to work the way you described.