As of 1.21.1, 100 and later:

/lootr - command usage (includes all block-based sub commands for spawning containers, such as chest, barrel, etc)

/lootr <type> (<table>) - these are defined by add-ons. Default include: chest, barrel, trapped_chest, shulker, pot, gravel, sand, cart, etc. Allows you to create the relevant block. Table is optional, one will be automatically selected, and allows auto-completion.

/lootr clear <player> - clear the stored inventories for the player <player>

/lootr cclear <entity selector> - as above, but allows you to use entity selectors such as @p, etc.

/lootr custom-chest - allows you to create a custom inventory, see Custom Containers and Maps

/lootr custom-area - allows you to create custom inventories in an area, see Custom Containers and Maps

/lootr custom-map <level> - allows you convert all chests/barrels into custom inventories for maps, Custom Containers and Maps

/lootr open_as <player> - allows you to open the chest you are standing on as the specified player

/lootr open_as_uuid <uuid> - allows you to open the chest you are standing on as the specified player via their user ID

/lootr id - shows you the unique ID of the inventory you're standign on

/lootr refresh - (deprecated, do not use)

/lootr decay - (deprecated, do not use)

/lootr openers - shows a list of people who have opened this container and thus have been scored; this list is consistent even if the contents (inventories) are reset

/lootr force_chunk - forces all block entities within the current chunk (that the source is in) to be added to the processing queue again

/lootr force_radius <radius> - forces all block entities within the current chunk and a radius around it (square) to be added to the processing queue again

/lootr force_all - forces all block entities within every current chunk that is loaded to be added to the processing queue (use sparingly)

For 1.16.5 and later:

/lootr - command usage

/lootr barrel - creates a barrel with a random loot table

/lootr barrel <table> - allows the selection of the loot table (auto-completes)

/lootr trapped_chest - creates a trapped chest with a random loot table

/lootr trapped_chest <table> - allows the selection of the loot table (auto-complete)

/lootr chest - creates a chest with a random loot table

/lootr chest <table> - allows the selection of the loot table (auto-complete)

/lootr shulker - creates a shulker box with a random loot table

/lootr shulker <table> - allows the selection of the loot table (auto-complete)

/lootr clear <player> - allows you to clear all saved loot tables (auto-complete from online players)

/lootr cart - creates a minecart with chest with a random loot table

/lootr cart <table> - allows the selection of the loot table (auto-complete)

/lootr custom - converts an inventory (1.21 and onwards: tagged blocks, earlier: chests and barrels) that the player is standing on into a custom inventory

/lootr open_as <player> - allows you to open a container as though you were another player. (since 1.20)

/lootr open_as_uuid <uuid> - allows you to open a container as though you were another player, providing their UUID rather than the player name. (since 1.20)

/lootr id - provides the unique identifier for the container that the player is standing on

/lootr refresh - marks the container the player is standing on to be refreshed based on the refresh_duration configuration option.

/lootr decay - marks the container the player is standing on to be decayed based on the decay_duration configuration option.

/lootr openers <location> - lists the UUID and player names of people who have looted the chest at the current location (use relative coordinates)

/lootr convert <startx> <starty> <startz> <stopx> <stopy> <stopz> - converts all containers that are eligible (lootr:convert/custom_eligible) within the confines specified into custom containers. (since 1.21)