WowAce

While running Onebag (3.11.1) in TBC I only get a popout of 2x6 bags when reviewing equipped bags. I have to disable Onebag to see that I have a 7th bag slot and to equip a bag to that sot. Once Equipped Onebank functions and shows the contents of that bag without issue, but I'm unable to increase the bag size because the bag isn't present within the bag frame with the other bags.

In the screenshot you can see the bags organized using bag break. You can see the main Bank and 7 groups of bags, however  in the Upper left you only see 6 bags presented as options to the player to swap bags in or out. There is no visible option that extends or adds that last bag to this frame.

https://imgur.com/a/ypuHBaX

Edit.

There are no Lua Errors when interacting with this last bag or storing items, stacks, or anything in it.

Looking through the code it seems to be in this loop here where it's maximum is hard coded into the loop of the function self.sidebar:SetScript("OnShow", function()

self.sidebar:SetScript("OnShow", function()
		if not self.sidebar.buttons then
			self.sidebar.buttons = {}

			for row=1, 3 do
				local b1ID, b2ID = row * 2 - 1, row * 2
				local yOffset = 0 - 10 - ((row - 1) * self.rowHeight)

This will only ever generate a 3 rows of 2 buttons each which means we are missing a button, additionally you are registering/creating 2 buttons per row so simply modifying the loop to create that last row will work but throw an exception for button2 in that 4th row as it's not actually valid.

This can be mitigated by adjusting the OnShow Function for TBC, however this will need to be revisted to be workable with existing classic code.

Example of manual fix listed below. https://imgur.com/a/tmPs6Sl

local sidebarRows = self.IsRetail and 4 or 3

	self.sidebar:CustomizeFrame(self.db.profile)
	self.sidebar:SetHeight(sidebarRows * self.rowHeight + self.bottomBorder + self.topBorder + 24)
	self.sidebar:SetWidth(2 * self.colWidth + self.leftBorder + self.rightBorder)

	self.sidebar:SetScript("OnShow", function()
		if not self.sidebar.buttons then
			self.sidebar.buttons = {}

			for row=1, 4 do
				local b1ID, b2ID = row * 2 - 1, row * 2
				local yOffset = 0 - 10 - ((row - 1) * self.rowHeight)

				local button = self:CreateBagButton(b1ID, self.sidebar)
				button:ClearAllPoints()
				button:SetPoint("TOPLEFT", self.sidebar, "TOPLEFT", self.leftBorder, yOffset)
				self.sidebar.buttons[b1ID] = button

				if (row < 4) then
					local button2 = self:CreateBagButton(b2ID, self.sidebar)
					button2:ClearAllPoints()
					button2:SetPoint("TOPLEFT", self.sidebar, "TOPLEFT", self.leftBorder + self.colWidth , yOffset)
					self.sidebar.buttons[b2ID] = button2
				end

			end

            if self.IsRetail then
                local button = self:CreateBagButton(7, self.sidebar)
                button:ClearAllPoints()
                button:SetPoint("TOP", self.sidebar, "TOP", 0, 0 - 10 - (3 * self.rowHeight))
                self.sidebar.buttons[7] = button
			end

			for _, button in pairs(self.sidebar.buttons) do
				BankFrameItemButton_Update(button)
			end
		end