These are options in the DXF/DWG Translation Setup dialog box. The available options will vary depending on the language version of ARCHICAD you are using.
Custom Functions contains add-ons for both Open Extras and Save Extras operations. Several functions are loaded by default; you need only turn them on or off using the checkboxes.
For example, the Store original Blocks add-on, if checked, will optimize the roundtrip of DWG files to and from ARCHICAD. Original blocks will be stored, so that unmodified DWG blocks, once reexported from ARCHICAD, will remain intact; no unnecessary new blocks will be created.
To change the order in which they are executed, you can drag and drop them to new locations within their element groups.
A Path area displays the location of the add-on. If you add further functions or delete any of them, you must press the Reload Functions button to refresh the function list. Custom function files are located in your ARCHICAD folder, under Add-Ons > Import/ Export.