[circonian]

I would imagine everyone probably does about the same thing. I think the only options would be to hook the setupCallback of the inventory row controls or just change the datatype for the pool and use your own template (which would be more work and unnecessary for just adding an icon & it would probably mess every other addon up).

Here is what I do if it helps any:
Hook into the inventories row control setupCallback (this is for: backpack, bank, guildBank, but not the quest inventory)

Warning: Spoiler

local function SetInventoryRowCallbacks()
    -- Loop through each inventory
    for k,v in pairs(PLAYER_INVENTORY.inventories) do
        -- as long as the dataType exists & the listView is not the quest inventory
        if (v.listView.dataTypes[1] and (v.listView:GetName() ~= "ZO_PlayerInventoryQuest")) then
            -- save the current setupCallback for the row controls
            local origCallback = v.listView.dataTypes[1].setupCallback              
            
            -- Create a new setupCallback for the row controls
            v.listView.dataTypes[1].setupCallback = function(invRowControl, ...)    
                    -- call your function to create an icon for this row
                    CreateResearchIcon(invRowControl)
                    CreateDestroyButton(invRowControl)  
                    -- call the original callback for the row control               
                    origCallback(invRowControl, ...)
                end             
        end
    end
end

Create the icon (actually a button in this example):

Warning: Spoiler

local function CreateDestroyButton(_cInvRowControl)
    if not (_cInvRowControl and _cInvRowControl.dataEntry and _cInvRowControl.dataEntry.data) then return end
    
    -- "Try" to grab the icon control you are wanting, It may already exist or not
    local cCntrlIcon    = _cInvRowControl:GetNamedChild("JunkItDestroyBtn")
    
    -- Grab whatever other info you need
    local iIconSize     = JunkIt.iconSize
    local cCntrlName    = _cInvRowControl:GetNamedChild("Name")
    local iBagId        = _cInvRowControl.dataEntry.data.bagId
    local iSlotId       = _cInvRowControl.dataEntry.data.slotIndex
 
    
    -- If the icon doesn't exist, create it --
    if(not cCntrlIcon) then
        cCntrlIcon = WINDOW_MANAGER:CreateControl(_cInvRowControl:GetName() .. "JunkItDestroyBtn", _cInvRowControl, CT_BUTTON)
        -- Setup the icon: size, anchor, dimensions, handlers, whatever
        cCntrlIcon:SetDimensions(iIconSize, iIconSize)
        cCntrlIcon:ClearAnchors()
        cCntrlIcon:SetAnchor(TOPLEFT, cCntrlName, TOPRIGHT, JunkIt.SavedVariables["INFOBUTTONOFFSETX"], 0)
        cCntrlIcon:SetDrawLevel(1)
        cCntrlIcon:SetNormalTexture(JunkIt.iconDestroy)
        cCntrlIcon:SetHandler("OnClicked", function() DestoyItem(_cInvRowControl) end)
        cCntrlIcon:SetClickSound("Click")
    end
    
    -- Do whatever code you need to decide if it should be hidden or not
    -- This one is actually a button, so it gets enabled/disabled as well
    if (IsItemJunk(iBagId, iSlotId) and JunkIt.SavedVariables["JUNKDESTROYER"]) then 
        cCntrlIcon:SetHidden(false)
        cCntrlIcon:SetEnabled(true) 
    else
        cCntrlIcon:SetHidden(true)
        cCntrlIcon:SetEnabled(false)
    end
    
end