It should be noted that these programs may or may not stop the carve immediately. Most of the sender programs that I have used do not use feed hold/cycle start, but just stop filling the grbl input buffer. grbl will continue to execute until the input buffer is empty with possible loss of position and/or state.
If you use the feed hold/cycle start hardware switches that is an immediate stop without loss of position or data. Also the grbl immediate software commands are an immediate halt without loss of position or data.
Either method for pausing the carve (switches or feed hold) may or may not have the parking code active based on a config.h setting.
The X-Controller has buttons for these functions.