Can you make you own themes?

[Steve B F 0]

Just wondering if you can make your own themes from a template from the themes folder?  If so any ideas how.

[theoldarchiver 54]

There is no (public) documentation on how to do that, and what special properties have to be set to make it a valid theme file.
It used to be easier in Toast 7 or earlier, but I gave up for the recent versions.