What's up, RMers?

[DerVVulfman]

Quick question: in which RMXP .rxdata files are switches and variables stored?

Kyonides is correct.  And for clarification, here are two sections of the default scripts:

Within the 'write_save_data' method of Scene_Save

    # Save magic number
    # (A random value will be written each time saving with editor)
    $game_system.magic_number = $data_system.magic_number
    # Write each type of game object
    Marshal.dump($game_system, file)
    Marshal.dump($game_switches, file)
    Marshal.dump($game_variables, file)
    Marshal.dump($game_self_switches, file)
    Marshal.dump($game_screen, file)
    Marshal.dump($game_actors, file)
    Marshal.dump($game_party, file)
    Marshal.dump($game_troop, file)
    Marshal.dump($game_map, file)
    Marshal.dump($game_player, file)

Within the 'read_save_data' method of Scene_Load

    # Read frame count for measuring play time
    Graphics.frame_count = Marshal.load(file)
    # Read each type of game object[/color]
    $game_system        = Marshal.load(file)
    $game_switches      = Marshal.load(file)
    $game_variables    = Marshal.load(file)
    $game_self_switches = Marshal.load(file)
    $game_screen        = Marshal.load(file)
    $game_actors        = Marshal.load(file)
    $game_party        = Marshal.load(file)
    $game_troop        = Marshal.load(file)
    $game_map          = Marshal.load(file)
    $game_player        = Marshal.load(file)
    # If magic number is different from when saving
    # (if editing was added with editor)
    if $game_system.magic_number != $data_system.magic_number

The values highlighted in red are obviously your switches and variables, and are stored within your save game.  The other values stored and loaded cover the condition of your actors, map position, and other data. And unless you're extremely good at scripting, its usually not good to touch these methods to add new data objects with their own tracking data.

However, I highlighted $game_system in pink... because its a usual go-to for scripters to add data into the Game_System class for custom script configuration values and feature-controlling data.