Corpses and F2

Corpses that fade away, and each player's own settings window.

GMod never removes corpses. Here they fade out after 30 seconds. NPC corpses (and a dead player's, until they respawn) are made by each player's own game, so each player picks the time themselves: F2 opens their settings window, "Corpses disappear after (s)" (0 = never; the client convar rpgx_corpse_time, saved on their PC). With sandbox's "Keep corpses" on (ai_serverragdolls 1) corpses are the server's instead, shared by everyone, and fade after rpgx_server_corpse_time.

Addons add rows to the F2 window on the client:

CreateClientConVar( "myaddon_volume", "50", true, false, "", 0, 100 )
GAMEMODE:AddClientSetting( { convar = "myaddon_volume", category = "Sound", text = "Volume", help = "0-100", min = 0, max = 100 } )