[spiel2001]

Yes... you can.

Use the command '/framestack' to enable the printing of frame names under the mouse and move your mouse over the "eye" so you can find out the name of the frame it is in. Then open [ Interface > AddOns > nUI > Plugins > nUI_BagBar.lua ] with any plain text editor (like notepad) and find the "Includes" section and add a line to it for the frame name that you want to move into the bag (see below). Save the file and reload nUI, it should move that frame into the button bag.

    -- buttons we want to force inclusion of
    
    Includes = 
    {        
        ["WIM_IconFrame"] = true,
        ["CTMod2_MinimapButton"] = true,
        ["PoisonerMinimapButton"] = true,
        ["GameTimeFrame"] = true,
        ["MobMapMinimapButtonFrame"] = true,
        ["BaudGearMinimapButton"] = true,
        ["name of the frame you want to add"] = true,
    },