Enhanced Stroke Builder
The Better Frame Borders widget gives you the ability to apply custom borders to your text and graphic frames in Muse.
There are 8 styles to choose from; each can be set to a different width and colour, or turned off completely, on each side of the frame. They also honour existing style presets, as well as the corner radius setting, so you can create curved edge frames as well as right-angles.
*This widget requires the latest version of Adobe Muse (2014.3)