After generating the input template using generate-template, you can edit input JSON file at any point of time in an interactive manner.

admin [ /migration ]$ tcamigctl edit-template -h 
usage: tcamigctl edit-template [-h] [-a] input_file 

Edits template file (usually generated using generate template command) to modify appliance details in the interactive mode 

positional arguments:   
   input_file      input file containing TCA manager and TCA-CP details 

options:   
  -h, --help       show this help message and exit   
  -a, --advanced  if specified, enables advanced configuration such as skipping vCenter details