Texts looks for Pandoc and XeLaTeX executables in the default locations. To use versions installed to other locations (e.g. via Cabal, MacPorts, Homebrew etc.) you can use the following commands.
defaults write io.texts.Texts TSPandocPath "/usr/local/bin/pandoc"
defaults write io.texts.Texts TSXelatexPath "/usr/texbin/xelatex"
Download and edit pandoc-path.reg or xelatex-path.reg.
Please contact support@texts.io if you have any questions.