mendo-export-tasks.js

console.log([...document.querySelectorAll('tr > td.solved:nth-child(1)')].map((el) => +el.innerText).join(';'));

mendo-load-unsolved.js

(
  (IMPORTED) => {
    IMPORTED
            .split(';')
            .map(x => +x)
      .filter(
                t => 
                    ![...document.querySelectorAll('tr > td.solved:nth-child(1)')]
                        .map((el) => +el.innerText)
                        .includes(t)
            )
      .map(
        t => 
          [
            ...document
              .querySelector(`.training-content > table:nth-child(1) > tbody:nth-child(2) > tr:nth-child(${t+1})`)
              .querySelectorAll("td")
          ]
            .map(t => {
                t.style["background-color"]="#FFDD55"
            })
      );
  }
)