Note: If you are using subtabs, tabFormat is used differently, but you still use the same format within each subtabs. See here for more on subtabs
Custom tab layouts can be used to do basically anything in a tab window, especially combined with the "style" layer feature. The tabFormat feature is an array of things, like this:
tabFormat: ["main-display",
["prestige-button", function(){return "Melt your points into "}],
"blank",
["display-text",
function() {return 'I have ' + format(player.points) + ' pointy points!'},
{"color": "red", "font-size": "32px", "font-family": "Comic Sans MS"}],
"blank",
["toggle", ["c", "beep"]],
"milestones", "blank", "blank", "upgrades"]
It is a list of components, which can be either just a name, or an array with arguments. If it's an array, the first item is the name of the component, the second is the data passed into it, and the third (optional) applies a CSS style to it with a "CSS object", where the keys are CSS attributes.
These are the existing components, but you can create more in v.js:
display-text: Displays some text (can use basic HTML). The argument is the text to display. It can also be a function that returns updating text.
raw-html: Displays some basic HTML, can also be a function.
blank: Adds empty space. The default dimensions are 8px x 17px. The argument changes the dimensions. If it's a single value (e.g. "20px"), that determines the height. If you have a pair of arguments, the first is width and the second is height.
row: Display a list of components horizontally. The argument is an array of components in the tab layout format.
column: Display a list of components vertically. The argument is an array of components in the tab layout format. This is useful to display columns within a row.
main-display: The text that displays the main currency for the layer and its effects.
resource-display: The text that displays the currency that this layer is based on, as well as the best and/or total values for this layer's prestige currency (if they are put in startData for this layer)
prestige-button: The argument is a string that the prestige button should say before the amount of currency you will gain. It can also be a function that returns updating text.
upgrades, milestones, challs, achievements: Display the upgrades, milestones, and challenges for a layer, as appropriate.
buyables, clickables: Display all of the buyables/clickables for this layer, as appropriate. The argument optional, and is the size of the boxes in pixels.
microtabs: Display a set of subtabs for an area. The argument is the name of the set of microtabs in the "microtabs" feature.
bar: Display a bar. The argument is the id of the bar to display.
infobox: Display an infobox. The argument is the id of the infobox to display.
toggle: A toggle button that toggles a bool value. The data is a pair that identifies what bool to toggle, [layer, id]
The rest of the components are sub-components. They can be used just like other components, but are typically part of another component.
upgrade, milestone, chall, buyable, clickable, achievement: An individual upgrade, challenge, etc. The argument is the id. This can be used if you want to have upgrades split up across multiple subtabs, for example.
respec-button, master-button: The respec and master buttons for buyables and clickables, respectively.
sell-one, sell-all: The "sell one" and "sell all" for buyables, respectively. The argument is the id of the buyable.