I'm new to Lyx, so these might not be elegant solutions. Another Lyx user helped me last week, so here is my attempt to pass on the favor.
-------------- To put a double space between chapter headings and section headings in the ToC: Put in the preamble: \usepackage{tocloft} Put underneath your chapter titles (in the body of your text) in ERT (Ctrl-L): \addtocontents{toc}{\vspace{0.35cm}\endgraf} --------------- To change to single spacing in a section, put this in ERT (Ctrl-L) before the section: \begin{spacing}{1} and then this in ERT after the section: \end{spacing} ---------------- I don't know if this is the text you mean, but to change the chapter heading text size, you will have to put something like this in the preamble: \chapterfont{\centering\normalfont\large\bfseries} I hope this is helpful.