This addon adds a Downloads toolbar button which opens the downloads window.
To install the addon go to releases and click on the .xpi file or download and drag it to the browser window.
For Firefox 57+ you should install the addon in the Nightly version of the browser. Before installation the browser needs to be configured to allow unsigned legacy addons.
See this tutorial for details on how to use legacy addons in Firefox Nightly edition: Install Legacy Addons in Firefox Nightly 57+.
In short the steps are the following:
- install Nightly edition and create a new Firefox profile for it if you want
- enable legacy addons setting
about:config?filter=extensions.legacy.enabled
preference totrue
- enable unsigned addons setting
about:config?filter=xpinstall.signatures.required
preference tofalse
- disable multiprocess mode if the addon gives errors setting
about:config?filter=browser.tabs.remote.autostart
tofalse