An explanation of custom colouring for themers is
HERE.
More on tinttcp in the Reaper.ini and rtconfig.txt files, and the associated preferences grey out,
HERE.
An explanation of how folder indenting in the TCP works is
HERE.
Using layout_dpi_translate to change layouts for HiDPI :
HERE
Adjusting themes using scripting :
HERE.
Adding theme adjuster functionality to a theme without doing any scripting :
HERE.