Credit where Credit is Due
This ability was requested by Imakefood on these forums.
WOW 5.2.0 with nUI+ 5.07.29
nUI by default does not display the grid frame regardless of the game settings to display buttons always. Possibly an oversight but just as likely an intended function.
However, with this addon you are able to ask nUI to permanently display or not display the gridlines on the bars as you require.
When the addon is first installed it may not reflect the interface options immediately. Either check the option and reload/relog or just wait for your next log in session.
Simply set the Always Show Action Bars option in the Interface->Action Bars options page and it will react accordingly with the buttons nUI sets up.
btn_size = 75, --53.5,
gap = 2,
anchor = "BOTTOM",
xOfs = 0,
yOfs = 123,
rows = 1,
cols = 12,
page = 1,
nuibind = "nUI_ACTIONBAR",
binding = "ACTIONBUTTON",
label = nUI_L["nUI_ActionBar"],