Is it possible to make custom maps?
Hello. Yes, but it a bit complicated. download rexuiz map creator/editor https://github.com/kasymovga/rexradiant/releases/tag/rexradiant-20240713
and try to enjoy. these must be manual for gtkradian/netradian and etc. its a similar editors made for different games.
Its also possible to create maps in blender, google for "quake 3 maps blender"