Would love a feature to auto-like videos from channels I'm subscribed to when I'm viewing them. I tend to forget or be busy with something else while watching videos.

Here, you want this extension for that: https://addons.opera.com/en/extensions/details/youtube-like-dislike-shortcut/ it has that exact feature you want, and then some.

It will auto Consent to videos, it will auto click the I Understand and auto click No Thanks for the free trial.

((a, t) => {

  let waitTime = 10; //how many seconds to wait for any sign-in popup to appear after fresh-loading a web page

  switch (location.hostname) {
    case "consent.youtube.com":
      if (a = document.querySelector('[type="submit"]')) a.click();
      break;
    case "www.youtube.com":
      addEventListener("load", h => {
        t = (new Date).getTime();
        h = setInterval(() => {
          if (a = document.querySelector('yt-upsell-dialog-renderer tp-yt-paper-button[aria-label="No thanks"]')) a.click();
          if (a = document.querySelector('yt-button-renderer tp-yt-paper-button[aria-label="I understand and wish to proceed"]')) a.click();
          if (((new Date).getTime() - t) > (waitTime * 1000)) clearInterval(h)
        }, 100);
      })
  }
})()