Keyvalues

"New map name", map :

Name of the map to switch to.

"Landmark name", landmark :

Landmark used to work as an orientation point between two maps in a center of both trigger_changelevels of maps.
It doesn't work in Sven Co-op, cause players starts at spawn points normally when new map loads. 

"Player take inventory to new map", keep_inventory :

If set to "Yes", player's ammo, armor and weapons are carried to target map.

"Change Target", changetarget :

The purpose of this key is unknown- multiple tests and half an hour on google brings no answers. Still, it is not required.

"Delay before change target", changedelay :

Delays "Change Target" action, whatever that action does.

"Percentage of players needed", percent_of_players :

Percentage of total amount of players needed to reach this point in order for level change.

Inventory Rules, InventoryRules @BaseClass:

List of inventory-related keyvalues used with item_inventory entity. Whenever player is attempting to use an entity, the inventory test runs. If test result is negative, the entity won't work. In other case, entity can be used as normal, but only by player who passed the test with required inventory conditions:

• "Inventory: Need item(s)", item_name_required : Item(s) (names separated by spaces) required to use this entity. 
  Refers to "Item name" value of item_inventory.
  
  
• "Inventory: Need item(s) from group(s)", item_group_required : Groups (separated by spaces), in which carried items belong to, required to use this entity. Refers to "Item group name" value of item_inventory.
  
  
• "Inventory: Item count in group need have", item_group_required_num : Minimal number of items, that belong 
  to specified group, required to use this entity. Use with "Inventory: Need item(s) from group(s)" keyvalue. Value of '0' means that all items from current group are required.
  
  
• "Inventory: CAN'T have item", item_name_canthave : Items in player inventory that will fail the test, and disallow usage 
  of this entity. Refers to "Item name" value of item_inventory.
  
  
• "Inventory: CAN'T have item from group", item_group_canthave : Items in player inventory, which belong to specified group, that will fail the test, and disallow usage of this entity. Refers to "Item group name" value of item_inventory.
  
  
• "Inventory: Item count in group CAN'T have", item_group_canthave_num : Minimal number of items in player inventory, which belong to specified group, that will fail the test, and disallow usage of this entity. Refers to "Item group name" 
  value of item_inventory. Value of '0' means no single item from current group should be equipped to pass the test.
  
  
• "On pass: Ignore item's on use triggers?", pass_ignore_use_triggers : If set to 'Yes' item's trigger targets from 'Target: On use (by trigger)' will not be fired when item is used by this entity.
  
  
• "On pass: Drop item(s)", pass_drop_item_name : Items to force-drop when the test result is positive, and entity is used successfully. Refers to "Item name" value of item_inventory. Multiple item names are separated by spaces.
  
  
• "On pass: Drop item(s) from group(s)", pass_drop_item_group : Items to force-drop, that belong to specified group, when the test result is positive, and entity is used successfully. All items from this group will be dropped. 
  Refers to "Item group name" value of item_inventory. Multiple item names are separated by spaces.
  
  
• "On pass: Ignore item's on drop triggers?", pass_ignore_drop_triggers : If set to 'Yes' item's trigger targets from 'Target: On drop' will not be fired when item is dropped by this entity with 'Drop items(s)' events above.
  
  
• "On pass: Return item(s)", pass_return_item_name : Items to return to their starting positions when test result is positive. Refers to "Item name" value of item_inventory. Multiple item names are separated by spaces.
  
  
• "On pass: Return item(s) from group(s)", pass_return_item_group : Items, that belong to specified group, to return to their starting positions when test result is positive. All items from this group will be returned. Refers to "Item group name" value of item_inventory. Multiple group names are separated by spaces.
  
  
• "On pass: Ignore item's on return triggers?", pass_ignore_return_triggers : If set to 'Yes' item's trigger targets from 'Target: On return' will not be fired when item is returned by this entity with 'Return items(s)' events above.
  
  
• "On pass: Destroy item(s)", pass_destroy_item_name : Items to remove when test result is positive. Refers to "Item name" value of item_inventory. Multiple item names are separated by spaces.
  
  
• "On pass: Destroy item(s) from group(s)", pass_destroy_item_group : Items, that belong to specified group, to remove when test result is positive. All items from this group will be removed. Refers to "Item group name" value 
  of item_inventory. Multiple group names are separated by spaces.
  
  
• "On pass: Ignore item's on destroy triggers?", pass_ignore_destroy_triggers : If set to 'Yes' item's trigger targets from 'Target: On Destroy' will not be fired when item is destroyed by this entity with 'Destroy items(s)' events above.
  
  
• "Target: Inventory rules failed", target_on_fail : Entity to trigger whenever test result is negative.
  
  

missing in FGD, master :

Put the name of a multisource entity to disable this trigger until multisource is triggered by all entities that targets mutlisource.

Flags

1: "No Intermission": This flag doesn't seems to change anything. Beer for the first person who explain this flag (if it's any usable).

2: "USE Only": Cause trigger_changelevel to work like point entity, which means it need to be triggered to perform map change.

4: "No CVAR Override": Do not override CVARs of destination map.