Release proxy settings back to browser after browser.proxy.settings.set()?

I am writing an extension that allows for fast adding of proxy servers to a list and fast switching between them, but my add on, once used to set ff’s proxy server, takes over as the proxy manager for ff. I want to release management back to the browser when a user of my addon isn’t using a proxy server from the addon. Is this possible? Essentially, I’m want to do this:

if user selects to use proxy from addon list
    set browser proxy server to manual with relevant details
end if
if user selects to stop using proxy from addon list
    let the browser manage proxy settings until user selects a new server from addon list
end if

the problem is, once a user selects to use a server from the addon list, the about:preferences says this and i can’t set any proxy settings through about:preferences anymore:

An extension is controlling how Firefox is connecting to the internet

And all the proxy settings are greyed out.

Is there a way to release control back to the browser?