[circonian]

This code is unnecessary:

Warning: Spoiler

local tradingHouseHiddenColumns = { statValue = true, age = true }
local zorgGetTabFilterInfo = PLAYER_INVENTORY.GetTabFilterInfo
 
function PLAYER_INVENTORY:GetTabFilterInfo(inventoryType, tabControl)
    if libCIF._tradingHouseModeEnabled then
        local filterType, activeTabText = zorgGetTabFilterInfo(self, inventoryType, tabControl)
        return filterType, activeTabText, tradingHouseHiddenColumns
    else
        return zorgGetTabFilterInfo(self, inventoryType, tabControl)
    end
end

Those columns are already hidden. If your seeing them then some other addon is messing it up:

Warning: Spoiler

-- These are already defined:
local tradingHouseHiddenColumns =
{
    ["statValue"] = true,
    ["age"] = true,
}
-- this gets called:
CreateNewTabFilterData(TradingHouseFilter, INVENTORY_BACKPACK, "", "", "", tradingHouseHiddenColumns),
 
local function CreateNewTabFilterData(filterType, inventoryType, normal, pressed, highlight, hiddenColumns)  
   ...
    local tabData = 
    {
        -- Custom data
        filterType = filterType,
        inventoryType = inventoryType,
        hiddenColumns = hiddenColumns,
-- which sets the hidden columns there
   ...
end

Bug? Or are you only counting on me to call this function in FilterIt?

-- What if multiple addons call this:
function libCIF:addBackpackLayoutShiftY(shiftY)
    libCIF._backpackLayoutShiftY = (libCIF._backpackLayoutShiftY or 0) + shiftY
end
libCIF._backpackLayoutShiftY = nil 
libCIF:addBackpackLayoutShiftY(40) -- now its 40
libCIF:addBackpackLayoutShiftY(40) -- now 80
libCIF:addBackpackLayoutShiftY(40) -- now 120

Are we sure these items you left out aren't needed anywhere else?
I know that currentFilter = TradingHouseFilter is used in ShouldAddSlotToList(..) to filter out bound items...although we are breaking that by allowing the menu bar to be shown & buttons to be clicked (yes we also fixed it by adding to the additional filter to hide bound items), but are we sure its not also needed somewhere else? What about code we don't have access to?

Warning: Spoiler

function ZO_InventoryManager:SetTradingHouseModeEnabled(enabled)
    local inventory = self.inventories[INVENTORY_BACKPACK]
 
    if(enabled) then    
        inventory.previousFilter = inventory.currentFilter
        inventory.currentFilter = TradingHouseFilter
    else
        inventory.currentFilter = inventory.previousFilter or ITEMFILTERTYPE_ALL
        inventory.previousFilter = nil
    end
 
    ZO_PlayerInventorySearchBox:SetHidden(not enabled)
    ZO_PlayerInventoryTabs:SetHidden(enabled)
    ZO_MenuBar_SelectDescriptor(inventory.filterBar, inventory.currentFilter)
end

This may be trivial, but by leaving those out it prevents code from knowing which btn was previously selected & returning to it. By saving the current filter, then reloading it, & then calling ZO_MenuBar_SelectDescriptor(inventory.filterBar, inventory.currentFilter) It returns the menu bar to its previously selected descriptor.