In the sample below, I simply print the states of those lines to the session system log (Menu -> View -> System Log). Feel free to change it according to the requirements of your script.

import "io_base.jncx"
import "io_Serial.jnc"
import "Serial/SerialLogRecordCode.jnc"

bool g_rts;
bool g_cts;

void onLogRecord(
	uint64_t timestamp,
	uint64_t recordCode,
	void const* p,
	size_t size
) {
	switch (recordCode) {
	case SerialLogRecordCode.PortOpened:
		SerialOpenParams const* params = (SerialOpenParams const*)p;
		g_rts = params.m_rts;
		g_cts = (params.m_statusLines & io.SerialStatusLines.Cts) != 0;
		printf("Initial RTS: %d CTS: %d\n", g_rts, g_cts);
		break;

	case SerialLogRecordCode.RtsChanged:
		g_rts = *(bool const*) p;
		printf("RTS changed: %d\n", g_rts);
		break;

	case SerialLogRecordCode.StatusLineChanged:
		SerialStatusLineChangedParams const* params = (SerialStatusLineChangedParams const*)p;
		if (params.m_mask & io.SerialStatusLines.Cts) {
			g_cts = (params.m_lines & io.SerialStatusLines.Cts) != 0;
			printf("CTS changed: %d\n", g_cts);
		}
		
		break;
	}
}

Well, in building test benches, keeping an eye on things like total bytes, throughput and status of lines like DSR/DTR and even RTS and CTS (when they are used as IO) is important.

Right. The proper way of getting notifications about all of these events is through the onLogRecord callback. Every time a new record appears in the log, your onLogRecord is called; you analyze the recordCode and react accordingly.

I still don't see the benefit of reading these values from the "Information" pane -- they are updated on-timer and are generally not in-sync with your onLogRecordCode.

Although I don't need information like CRC things, but I assume for other use cases accessing that can be useful.

Checksums in the "Information" pane are updated when a user manually selects ranges in the log. In other words, they are updated based on UI events, and as such, they can't be relied upon from scripts. If checksums are important for your script, you must calculate them in your onLogRecord (e.g., using helper functions in files like scripts/common/crc16.jnc).