local function createMyTab()
local tab = vgui.Create("whatever...")
-- Create the your tab here or something
return tab
end
hook.Add("F4MenuTabs", "addTab", function()
-- Add the tab to F4 (will be added as the last tab)
-- DarkRP.addF4MenuTab("NAME OF TAB HERE", vguiControlOfTab) returns the tab number of the added tab
local tabNr = DarkRP.addF4MenuTab("My Custom Tab", createMyTab())
-- If you want it to move the tab to be before another, use this
-- DarkRP.switchTabOrder(TabNumberOfTabYouWantToMove, TabNumberOfDestination)
DarkRP.switchTabOrder(tabNr, 4)
end)