Running a test batch script results in an error "Could not open \\.\COM1. Serial port is in use or does not exist." See Figure 1 below.

Figure 1. Error: COM Port is not configured

Click on OK. The XMTR-MV will open. Go to Settings > Ports menu.

Figure 2. Settings Menu

Select the appropriate COM port. 

Figure 3. COM Port Settings

XMTR-MV configurations can be saved. Go to  File > Save As then specify a file name and directory to save the *.fdm configuration.  See Figure 4.

Figure 4. Save a Configuration

HINT: Update the INI file to store the COM Port setting for use later. Open the INI file stored in C:\HCF\DDL\HostTest\Xmtr and add an entry [App] followed by the key "ComPort=n", where n is the zero based number of the serial port (ie, 0 is Com1, 1 is Com2, 2 is Com3, etc). See Figure 5.

Figure 5. XMTR-MV INI File With COM Port 4 Saved By Default