Franjun,
For the first question, a good solution would be to use Enter as a Shortcut Key for the Send button (and you can set this botton to invisible if you do not want to see it on the panel). You can do this by using SetCtrlAttribute. Select, under the Control Attribute field, Shortcut Key and for the Attribute Value VAL_ENTER_VKEY. In this way, every time you press the Enter key, the string will be sent.
Now, for the second question there are different ways in which you can have multiple windows to communicate with different ports. The easiest way to do it would be by running eight executables. Each executable will be in charge of configuring a specific port. A second option would be to have a user interface with eight buttons. If a button is pressed, th
en you can launch an executable with the ANSI_C system() function, which will wait for the program to be executed. For example, if you pressed button 1, and then called system(serial.exe 1), the program would open the serial.exe file and configure port 1. The advantage of using this fuction is that you cannot access other ports while configuring one and at the same time, you would only need to have one executable instead of eight on the target machine. Now, if you want to use multiple ports at the same time, a good idea would be to use LaunchExecutable instead of System. Finally, remember that you will need to perform command-line processing if you use this method. Good luck!