Find duplicates links in OneTab

findDuplicatesInOnetab.js

(function findDuplicatesInOnetab() {
  const isOneTab = document
    .querySelector("title")
    ?.innerHTML.includes("OneTab"); // cheap OneTab check
  if (!isOneTab) {
    alert("Run this script in a OneTab tab");
    return;
  }

  const getOneTabLinks = () => [
    ...document.querySelectorAll("#contentAreaDiv [href]"),
  ];

  const getDuplicateLinks = (links) => {
    let linkList = links || getOneTabLinks();
    linkList = linkList.map((linkEl) => ({
      link: linkEl.getAttribute("href"),
      linkEl,
    }));
    const duplicateLinks = [];
    const groupedDuplicates = [];

    linkList.forEach(({ link, linkEl }, index) => {
      const alreadyFound = duplicateLinks.includes(link);
      if (alreadyFound) {
        return;
      }

      const foundDuplicateEls = linkList
        .filter(({ link: linkCompare }, indexCompare) => {
          const alreadyFound = duplicateLinks.includes(linkCompare);
          if (index === indexCompare || alreadyFound || link !== linkCompare) {
            return false;
          }
          return true;
        })
        .map(({ linkEl }) => linkEl);

      if (foundDuplicateEls.length) {
        duplicateLinks.push(link);
        groupedDuplicates.push({
          link,
          linkEls: [linkEl, ...foundDuplicateEls],
        });
      }
    });
    return groupedDuplicates;
  };

  const scrollToEl = (el) => {
    el.scrollIntoView({ behavior: "smooth", block: "center" });
  };

  const markLink = (el, text) => {
    el.style.backgroundColor = "#DE5918";
    el.style.color = "#fff";

    if (text) {
      const duplicateMarker = document.createElement("span");
      duplicateMarker.innerHTML = text;
      duplicateMarker.classList.add("duplicate-marker");
      duplicateMarker.style.marginRight = "20px";
      el.insertAdjacentElement("afterbegin", duplicateMarker);
    }
  };

  const unMarkLinks = (linkEls = getOneTabLinks()) => {
    linkEls.forEach((el) => {
      el.style.backgroundColor = undefined;
      el.style.color = undefined;

      const duplicateMarker = el.querySelector(".duplicate-marker");
      if (duplicateMarker) duplicateMarker.remove();
    });
  };

  const findDuplicates = (links) => {
    unMarkLinks(links);
    const groupedDuplicates = getDuplicateLinks(links);

    if (!groupedDuplicates.length) {
      alert("No Duplicates Found");
    } else {
      groupedDuplicates.forEach((duplicate, groupIndex) =>
        duplicate.linkEls.forEach((el, duplicateIndex) =>
          markLink(
            el,
            `${groupIndex + 1}/${groupedDuplicates.length} | ${
              duplicateIndex + 1
            }/${duplicate.linkEls.length}`
          )
        )
      );
      alert(`${groupedDuplicates.length} Duplicates Found`);
      scrollToEl(groupedDuplicates[0].linkEls[0]);
    }
  };

  findDuplicates(getOneTabLinks());
})();

Open Browser Console in OneTab paste script above.
After that run findDuplicatesInOnetab() in a new line.

EDIT: Rewrote the script. No need to run in a new line.
Simply paste the script in the browser console.
Might take a few seconds to process.
If you want to update the result you have to run the script again, but first remove the old result by refreshing the OneTab browser tab.

Hello, I've just used this and it worked very well, thank you for your work.