First I tried setting in Maestro Control Center SW, Speed = 10, Target = 1500. And then sent two commands manually in the serial port monitor sw. What I expected was, Servo could move from 1500 to 1900 and back to 1300 with speed = 10 (slow). (Please see pictures.)
You are not going to be able to send a string of commands just from your serial terminal program to move a single servo between several positions, since the servo will not have enough time to move to each position between position updates. You might be able to write a script for the Maestro and trigger it from your serial terminal program using the Restart Script at Subroutine command. You could also use the Restart Script at Subroutine with Parameter command if you want to specify the target positions from your program. You can find more details on those commands in the “Serial Script Commands” section of the Maestro User’s Guide. For the Maestro script, you should look at the code under the “Making smooth sequences with GET_MOVING_STATE” heading in the “Example scripts” section of the guide.