Red uses a subclass of discord.py's CommandTree object in order to allow Cog Creators to add application commands to their cogs without worrying about the command count limit and to support caching AppCommand objects. When an app command is added to the bot's tree, it will not show up in tree.get_commands or other similar methods unless the command is "enabled" with [p]slash enable (similar to "load"ing a cog) and tree.red_check_enabled has been run since the command was added to the tree.
Note
If you are adding app commands to the tree during load time, the loading process will call tree.red_check_enabled for your cog and its app commands. If you are adding app commands to the bot outside of load time, a call to tree.red_check_enabled after adding the commands is required to ensure the commands will appear properly.
If application commands from your cog show up in [p]slash list as enabled from an (unknown) cog and disabled from your cog at the same time, you did not follow the instructions above. You must manually call tree.red_check_enabled after adding the commands to the tree.
redbot.core.tree
RedTree