Opera GX has offered the possibility of using Mods, the latter allowing extensive customization of your browser. your mods can be found at opera://mods/ on your browser. if you want to use one Mod, the Mod Store is on this site. if you don't know how to create them, then this site is made for you!
there is two possibilities of using my Mods:
You can download one of my mods here, but your mods will not be easily updatable, and you'll have to reinstall the mod to get the latest release. After extracting the .zip file, you'll need to got to opera://extensions/ in your browser.
Then, if not already done, trigger this switch. 
after doing this, click here and select the extracted folder.
and... done! now you can use my mod.
the second possibility is a lot more simple, 'cause you'll can update it easily.
Go to this site, then search for the mod you want, and just click on the "install" button just here.
with this way, you'll can update it more easily in opera://extensions/, by clicking this button 
thanks for reading this! if you need some help, open an issue, or dm me on Discord, i'm a lot active. here's my pseudo : Wishrito