I have made a toolbar of some Foobar2000 command line commands.
I haven't attempted to implement any of these in @lxp's button yet.
The Foobar2000 icon is from @galaxyhub's Express Icon Set
The toolbar buttons use one folder alias.
A folder alias named Foobar2000 points to the folder that contains foobar2000.exe .
In my case it was C:\Program Files\foobar2000 .
The toolbar buttons also use three user commands.
Foobar_Playback.ouc (412 Bytes)
Foobar_Add.ouc (322 Bytes)
Foobar_Window.ouc (371 Bytes)
And here is the toolbar.
Foobar2000.dop (3.0 KB)
Edit: I don't know why this works, but I have found that /Foobar2000\foobar2000.exe /playing_command:Remove {filepath$} adds selected files to the playlist, playing the first one, and removes all other files from the playlist. However, /Foobar2000\foobar2000.exe /playing_command:Remove desn't seem to do anything at all.