Dear, As proposed in interface3.pdf, I hereby inform that in the next version of the wheelchart package, I plan to use some of the \tl_build_... functions from l3candidates. Namely \tl_build_begin:N \tl_build_end:N \tl_build_gbegin:N \tl_build_gend:N \tl_build_gput_left:Ne \tl_build_gput_right:Ne \tl_build_put_right:Ne \tl_build_put_right:Nn \tl_build_put_right:NV Kind regards, Matthias Floré