You should be able to add spaces in a straight/pivot table for example. In the dimensions tab add a calculated dimension and add ' ' & Dimension name. Works with if-statements as well, if you only want to indent some of the dimension values in your chart.
Chr(160) usually works where Chr(32) doesn't. Chr(160) is so called non-break space. If that fails there is a second option using Unicode space characters like Chr(8192) - a typographic space character.
Sometimes repeating the character ' ' is not enough to add spaces at the left for indentation because they are trimmed and ignored. In those cases, my workaround has been to repeat the tab character Chr(9) instead of ' ' to get the desired indentation.