Wiki add custom css

Hello friends!
I have created a customized sidebar on the wiki project documentation adding the _sidebar page and everything works great.
If I am not wrong, I read somewhere that in a similar way I could add _custom.css, in order to be able to add some customized css styles over the pages.
The reason why I want to do that, is because my sidebar expands up to 5 levels and I need the width to adjust automatically. I would like to add just the code similar as following:

.right-sidebar {
    width: auto;
    max-width: 20%;
}

Could I get some help please?
Thanks in advance!

I don’t think the custom.css or custom.js feature is available at this moment. You can check this feature request thread and come up with couple of workaround:

Hi @swarnava, thank you for your reply. I am looking forward for any possible workaround.
Cheers.