It is possible to explicitly add values to the timeline by importing the XCPlayground framework and calling XCPCaptureValue with a value that should be displayed in the timeline. This takes an identifier, which is used both as the title and for group-related data values in the same series. When the value history button is selected, it essentially inserts a call to XCPCaptureValue with the value of the expression as the identifier.

For example, to add the logo to the timeline automatically:

import XCPlayground
XCPCaptureValue("logo",logo)

It is possible to use an identifier to group the data that is being shown in a loop with the identifier representing categories of...