What about code bases that have both Python and C files? This would require them to have two projects.
Also, I don't currently use geany's projects functionality at all (and that geany is still useful without its use is one of its good points) and don't wish to start.
So for the time being, I'll scrape by by changing the settings manually where necessary. Thankfully, the "Detect from file" option in the indentation configuration page usually works and it's usually only a problem when I create a new file.
Thanks for looking at this.