I don't like that's necessary to add a icon
You are forced to have all the stuff under the External Application Button. Not having that context menu would save us a click.
You can't rearrange the list of applications.

To open twitch streams using streamlink, in the Executable field you paste the path to streamlink.
C:\Program Files (x86)\Streamlink\bin\streamlink.exe
In the arguments field: [HREF] Best if you want to open the streams at best quality, [HREF] 480p if you want to open streams in 480 and so on..