Here's a simulation of the linkage, and the plans are below the video.
The diagrams below can get crowded and confusing. To hopefully make it less confusing the linkage is presented in two stages, starting with TrotBot's bar lengths without the retractable toe. Please note that the triangle's bottom right angle highlighted in pink is not 90 degrees, but is 109.475 degrees.
Below the retractable toe is added, and none of the above bar lengths or frame connection coordinates have changed. The following two images have the same bar lengths, but show them at different points in the crank's rotation.