Indeed, I would like to keep reals tabs by default and use spaces for a lot of
format like : .h, .c, .cc, .cpp, .klx(custom extension)

Set spaces as default inte program settings / Editor
Individual real tabs base on the highlighter (file type) are in 
Program settings / Highlighter settings / Specification tab for C++ highlighter
The check box has 3 states - Checked - ON, Unchecked OFF, square - set as
Program settings. 

If you hjave individual extension, add it into existing highlighter, for this
case I guess it will be new extension for C++ highlighter. Again on the same
place into file masks

PSPad freeware editor https://www.pspad.com

Odpovedet emailem