I've been using pyload here the past few weeks. Does mega.nz of course, plus a few other of those DDL sites. It also does youtube, but not nearly as well as youtube-dl... wish they'd use it as a backend.
I mean, giving this app a front-end is the right idea, but how the hell do I use it when I'm at work? Remote desktop connections (vnc or microsoft) are always flaky. Better off ssh-ing in and using the command line.
I like pyLoad more, has a webinterface and can run inside docker on a server. So it can download even when my pc is turned off. Used some greasemonkey browser scripts to get Click'N'Load working. I don't use it anymore though, i completely stopped OCH downloading.
When I had a 6 Mbps ADSL, I used to download stuff overnight through PyLoad on my Raspberry Pi.
I can highly recommend it. You input one or more URLs from the web frontend, and it downloads in the background.