public async sesc(): Promise<string> {
  this.requireAuthenticated();
  const response = await this.api.get(
    "https://bitcointalk.org/index.php?action=profile",
  );
  const $ = cheerio.load(await response.text());
  const logoutUrl = $(
    'td.maintab_back a[href*="index.php?action=logout;sesc="]',
  ).attr("href");
  const sesc = logoutUrl?.match(/sesc=(.*)/);
  if (sesc && sesc[1]) {
    return sesc[1];
  }
  throw new Error("Could not get sesc");
}

public async getProfile(userId?: ProfileUserId): Promise<Profile> {
  if (!userId) {
    this.requireAuthenticated();
  }

  const url = userId
    ? `https://bitcointalk.org/index.php?action=profile;u=${userId}`
    : "https://bitcointalk.org/index.php?action=profile";

  const response = await this.api.get(url);
  const html = await response.text();
  const $ = cheerio.load(html);

  const name = getTableRowValue($, "Name:");
  const posts = getTableRowValue($, "Posts:");
  const activity = getTableRowValue($, "Activity:");
  const merit = getTableRowValue($, "Merit:");
  const position = getTableRowValue($, "Position:");

  const profileUserId = $("a[href*=/index.php?action=merit;u=]").attr("href")
    ?.match(
      /\/index\.php\?action=merit;u=(\d+)/,
    )?.at(1);

  return {
    name,
    userId: Number(profileUserId),
    posts: Number(posts),
    activity: Number(activity),
    merit: Number(merit),
    position,
  };
}
  
  public async getProfileSettings() {
    this.requireAuthenticated();

    const response = await this.api.get(
      `https://bitcointalk.org/index.php?action=profile;sa=forumProfile`,
    );

    const html = await response.text();
    const $ = cheerio.load(html);

    const personalText = $(
      "#creator > table input[name=personalText]",
    ).attr("value")!;

    const birthYear = $("#creator > table input[name=bday3]").attr("value")!;
    const birthMonth = $("#creator > table input[name=bday1]").attr("value")!;
    const birthDay = $("#creator > table input[name=bday2]").attr("value")!;
    const location = $("#creator > table input[name=location]").attr("value")!;

    const gender = $([
      ...$(
        "#creator > table select[name=gender] > option",
      ),
    ].find((option) => $(option).attr("selected"))).attr("value") ?? 0;

    const ICQ = $("#creator > table input[name=ICQ]").attr("value")!;
    const AIM = $("#creator > table input[name=AIM]").attr("value")!;
    const MSN = $("#creator > table input[name=MSN]").attr("value")!;
    const YIM = $("#creator > table input[name=YIM]").attr("value")!;
    const signature = $("#creator > table textarea[name=signature]").text();
    const websiteTitle = $("#creator > table input[name=websiteTitle]").attr(
      "value",
    )!;
    const websiteUrl = $("#creator > table input[name=websiteUrl]").attr(
      "value",
    )!;
    const skype = $("#creator > table input[name='default_options[CP1]']").attr(
      "value",
    )!;
    const bitcoinAddress = $(
      "#creator > table input[namr='default_options[addr]']",
    ).attr("value")!;
    const otherContactInfo = $(
      $("#creator > table input[name='default_options[CP11]']"),
    ).attr("value")!;

    const showUntrustedFeedbackByDefault =
      $("#creator > table input.check[name='default_options[show_untrusted]']")
        .attr("checked") === "checked";
    const showPatrolLink =
      $("#creator > table input.check[name='default_options[showpatrol]']")
        .attr("checked") === "checked";

    const showPostCountByPosts =
      $("#creator > table input.check[name='default_options[showpostcount]']")
        .attr("checked") === "checked";

    const disableAds =
      $("#creator > table input.check[name='default_options[noads]']").attr(
        "checked",
      ) === "checked";

    const result = {
      personalText,
      birthYear: String(birthYear),
      birthMonth: String(birthMonth),
      birthDay: String(birthDay),
      location,
      gender: Number(gender),
      ICQ,
      AIM,
      MSN,
      YIM,
      signature,
      websiteTitle,
      websiteUrl,
      skype,
      bitcoinAddress,
      otherContactInfo,
      showUntrustedFeedbackByDefault,
      showPatrolLink,
      showPostCountByPosts,
      disableAds,
    };

    return result;
  }

  public async editProfile(data?: EditProfileData): Promise<boolean> {
    const currentSettings = await this.getProfileSettings();
    const profile = await this.getProfile();
    const sesc = await this.sesc();

    const body = new FormData();

    const fields: Record<string, string | number> = {
      personalText: data?.personalText ?? currentSettings.personalText,
      bday3: String(currentSettings.birthYear),
      bday2: String(currentSettings.birthDay),
      bday1: String(currentSettings.birthMonth),
      location: data?.location ?? currentSettings.location,
      gender: currentSettings.gender,
      ICQ: currentSettings.ICQ,
      AIM: currentSettings.AIM,
      MSN: currentSettings.MSN,
      YIM: currentSettings.YIM,
      signature: data?.signature ?? currentSettings.signature,
      websiteTitle: data?.websiteTitle ?? currentSettings.websiteTitle,
      websiteUrl: data?.websiteTitle ?? currentSettings.websiteUrl,
      "default_options[CP1]": currentSettings.skype,
      "default_options[addr]": data?.bitcoinAddress ??
        currentSettings.bitcoinAddress,
      "default_options[show_untrusted]": Number(
        currentSettings.showUntrustedFeedbackByDefault,
      ),
      "default_options[showpatrol]": Number(currentSettings.showPatrolLink),
      "default_options[showpostcount]": Number(
        currentSettings.showPostCountByPosts,
      ),
      "default_options[CP11]": currentSettings.otherContactInfo,
      "default_options[noads]": Number(currentSettings.disableAds),
      sc: sesc,
      userID: profile.userId,
      sa: "forumProfile",
    };

    for (const field in fields) {
      body.set(field, String(fields[field]));
    }

    await this.api.post(
      "https://bitcointalk.org/index.php?action=profile2",
      {
        body,
      },
    );

    return true;
  }

const forum = new BitcoinTalkApi();
await forum.auth({
  username: "TryNinja_BOT2",
  password: "xxxxxxxxxx",
  captchaCode: "xxxxxxxxx",
});

await forum.editProfile({ signature: "my signature bbcode here!" });

If I understood you correctly, you are talking about something like: