The chart showing different combinations of reveal, mirroring, and angle is wrong at https://gdl.graphisoft.com/reference-guide/doors-and-windows . The only one of these that changes the handedness/hinging/opening (L/R) of a door is SYMB_MIRRORED. The same type of illustration at https://gdl.graphisoft.com/gdl-basics/simple-doors-and-windows seems to be correct. It took me embarrassingly long to figure this out, trying to fathom what combination produces the images in the chart, before understanding that the chart itself was wrong...
On a higher level it would be better if this information could be found in one place without duplication, or that the GDL reference and GDL basics -tutorial would link to each other more. Sometimes one contains a relevant piece of information that is missing or not very well expressed in the other.
Is this forum now the primary place to report bugs like this? I think it would be better to have a separate bug reporting mechanism like we have in localization, or at least an address to send minor fixes to. If there is one, I couldn't find it on the site. No need for the whole GDL community to read about typos or broken links...
(Here's my reference to the different door orientation variables.)