Before directly answering your question, let's talk about the data hierarchy: Account, dict-level, data-level separated by commas as shown. The first element is the account, the second element is the dictionary level of the file which contains all of your attribute defining items and data-level file D-pointers. The third element is the data-level of the file.

To access the account itself, use the account name followed by two commas.

To access the dict of the file, use the literal "dict" followed by the account name followed by the file name followed by a comma like this:

LIST DICT SQLDEMO,CUSTOMERS,

To access the data level, use account name followed by comma followed by file name followed by comma as above without the "dict":

LIST SQLDEMO,CUSTOMERS,

This works when the dict and data lever bear the same name. D3 will gives you the ability to have several data levels for one dict level:

LIST SQLDEMO,CUSTOMERS,CUSTOMERS will give you the same output as above.
LIST SQLDEMO,CUSTOMERS,HISTORY will give you another CUSTOMERS data level.

If you are already in the account in question, you can eliminate the account-name reference like this
LIST CUSTOMERS
LIST CUSTOMERS,HISTORY

Now, back to your question:

LF MDS will show you all of the accounts and Q-poitners to accounts on D3 windows it will look like this:

Page 1 mds account file listing 07:12:18 17 Mar 2022
dict-name base mod

D3WATCHER 8325 47
dm 2564 47
mds 2451 3
spooler 8275 47

Synonym name Account File name

acme fsi:acme
agh-pgm fsi:agh-pgm
bscDev fsi:bscDev
compareAccounts fsi:compareAccounts
fh fsi:fh
fhb_util fsi:fhb_util

You can then see the files in the account using LF <accountname>,, to see the dictionary levels, something like this:

:lf sqldemo,,
Page 1 sqldemo account MD file listing 07:15:22 17 Mar 2022
dict-name base mod data-name base mod

abshbak N/A 1 abshbak N/A 47
absprod N/A 1 absprod N/A 47
apicapturelog N/A 1 apicapturelog N/A 101
auditlog N/A 1l auditlog N/A 1l

Hi, - my penny's worth.

One of the very first TCL commands in Pick (now D3) Iearnt was "LIST ONLY SYSTEM" which effectively in the DM account provided a list of all other Pick accounts in the DB.

If one then chooses a DB, say SQLDEMO, by executing a "TO SQLDEMO" to produce a list of tables (files) within SQLDEMO, the command to execute at TCL is "LISTFILES'