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You can modify this code to suit your needs, of course. For example, instead of calling Update() periodically, you can read channels only when you need them:

int offset_a = 0;
int offset_b = 0;

int ReadA()
{
    while (current_ch) Update();    // make sure channel A has been read
    return value_a - offset_a;
}

int ReadB()
{
    while (!current_ch) Update();   // make sure channel B has been read
    return value_b - offset_b;
}

// call this in the beginning of a program when sensors are in neutral position
void Tare()
{
    // reset previous offsets
    offset_a = 0;
    offset_b = 0;
    // read and discard to initialize chip gain
    ReadB(); 
    // store current values as new offsets
    offset_a = ReadA();
    offset_b = ReadB();
}

Here is some primitive code I've used before to read two load cells with one chip. All you have to do is call Update() function often enough to keep reading data.

Here is some primitive code I've used before to read two load cells with one chip. All you have to do is call Update() function often enough to keep reading data. You don't need any additional components for second load cell. Connect it as shown in the datasheet only use INB+, INB- inputs, there should not be much cross-talk between the channels.

UPDATE

Here is some primitive code I've used before to read two load cells with one chip. All you have to do is call Update() function often enough to keep reading data.

#define GAIN_A_128  1   // Gain 128 (channel A) +/- 20mV @5V
#define GAIN_B_32   2   // Gain 32 (channel B) +/- 80mV @5V
#define GAIN_A_64   3   // Gain 64 (channel A) +/- 40mV @5V

int32_t value_a = 0;
int32_t value_b = 0;
bool current_ch = false;    // channel a = true, channel b = false

int ReadAndSetGain(int gain)
{
    // read chip data
    int ret = 0;
    // pulse clock pin 24 times to read the data as 2's complement value
    for (int i = 0; i < 24; i++)
    {
        gpio_set(clk_out_pin, true);
        gpio_set(clk_out_pin, false);
        ret = (ret << 1) + (gpio_get(data_in_pin) ? 1 : 0);
    }
    // set the channel and gain factor for next reading using clock pin
    for (int i = 0; i < gain; i++)
    {
        gpio_set(clk_out_pin, true);
        gpio_set(clk_out_pin, false);
    }
    // propagate sign bit
    if (ret & 0x800000) ret |= 0xFF000000;
    return ret;
}

// Call this function every 13 ms if HX711 data rate is 80 Hz,
// every 101 ms if data rate is 10 Hz to keep channel values updated.
// Note that default gain after reset is GAIN_A_128, so the channel values
// will be incorrect until after three successful readings.
void Update()
{
    // make sure data is available
    if (gpio_get(data_in_pin)) return;
    if (current_ch) {   // reading channel A
        value_a = ReadAndSetGain(GAIN_B_32);
    } else {            // reading channel B
        value_b = ReadAndSetGain(GAIN_A_64);
    }
    current_ch = !current_ch;
}