My installation recognises the fonts I have installed in my system. For instance if I want to use Droid Sans Mono (provided by the fonts-droid package) I can set the font as driod sans mono, DrOiD SANS mono (i.e., the case doesn’t matter). It also works for the fonts located in ‘/home/user/.local/share/fonts’.
However, you cannot set the font weight; it will always use the regular version of each font. For instance let’s say I want to use Helvetica Neue LT Std Bold or Helvetica Neue LT Std 75 Bold Outline. Let the images speak by themselves:
Helvetica Neue LT Std, Helvetica Neue LT Std Bold, Helvetica Neue LT Std 75 Bold Outline
The conclusion is that what matters is the Family name, which you can easily know opening the corresponding .ttf or .otf font files (see the example below).