Right click on L4D2 on your library and select "properties" and "set launch options" and type in "-console", now open up l4d2 and the console should open.

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=675686554
subscribe to this addon.

type in console "map (map name) single_versus_with_bots (if you want to do this offline)"
put versus where single_versus_with_bots if you wish to do this on your own server with humans.

z_spawn
z_spawn hunter
z_spawn smoker
z_spawn boomer
z_spawn spitter
z_spawn jockey
z_spawn charger
z_spawn witch
z_spawn tank
director_force_panic_event

sv_cheats 1 required, commands for spawning any infected, the blank z_spawn spawns a common, director_force_panic_event spawns a horde.

enter the following commands in console (sv_cheats 1 required!):

z_jockey_limit 0
z_hunter_limit 0
z_spitter_limit 0
z_charger_limit 0
z_boomer_limit 0
z_smoker_limit 0

now you should have control where special infected spawn.

notes:
hunter and smoker limits reset to 1 when map changes, be sure to set their limits to 0 again.
Director still handles witches, tanks and hordes, you may remove witches or tank with ent_remove.

enter these commands now:

spec_allowroaming 1
jointeam 1

you'll switch to spectator mode and you'll be able to fly freely around the map, so you can spawn special infected and commons.

With this guide you have been granted partial director control in your own l4d2 server, leave any comments here if i missed anything!!