Create a backslash command alias
psql's backslash commands such as \dt (list tables) are compact and quick to type, however they are sometimes not always easy to remember. \dn comes to mind - it lists schemas (the more intuitive \ds lists sequences) - for a mnemonic, think of 'n' as standing for namespace.
Though it isn't possible to directly define your own more memorable aliases for backslash commands, psql's variable interpolation provides a handy workaround:
testdb=# \set list_schemas '\\dn' testdb=# :list_schemas List of schemas Name | Owner --------+---------- public | postgres (1 row)