A browser add-on to help you find a tab easier

https://addons.mozilla.org/en-CA/firefox/addon/find-your-tab/

You can enable or disable DoH in your Firefox connection settings:

1. Click the menu button and select Options.
2. In the General panel, scroll down to Network Settings and click the Settings… button.
3. In the dialog box that opens, scroll down to Enable DNS over HTTPS.

   • On: Select the Enable DNS over HTTPS checkbox. Select a provider or set up a custom provider.
   • Off: Deselect the Enable DNS over HTTPS checkbox.

   

4. Click OK to save your changes and close the window.

Source:

https://support.mozilla.org/en-US/kb/firefox-dns-over-https

The Web Developer extension adds various web developer tools to the browser.

https://addons.mozilla.org/en-US/firefox/addon/web-developer/

Ads just annoy me and I've never bought anything from an ad.

On YouTube, you have to listen then, no way, I will not waste minutes of my life waiting for ads.

AdBlocker for YouTube™ removes all annoying Ads from YouTube.
Important features:
1. Allows you to remove annoying contents from your YouTube videos.
2. You can also remove annotations from videos and musics (see options page).
3. Loads videos and YouTube website faster.
4. Supports both Firefox Desktop and Mobile (Android).

https://addons.mozilla.org/en-US/firefox/addon/adblock-for-youtube/