Can ksh on AIX be configured to use the tab key for filename completion?

I gather your shell is in vi mode. Not sure this will work, as my AIX knowledge is limited, but yu can try to add this to your profile:

set -o emacs
bind "^I=complete"

Google says that ksh in AIX is kinda crippled from this point of view, so maybe bash would be a better bet.

See if /usr/bin/ksh93 is available:

ksh93 --version

If it says

version         sh (AT&T Research)

then use that as your interactive shell. It will have the ${.sh.version} and should have the TAB expansion.

There is an alternative for this question.

First set vi mode for ksh:

$ set -o vi

After, you can use the Tab key this way. Example: You want complete the next path:

$ cd /usr/local/s

Type Tab key twice and You will see this:

$ cd /usr/local/s
1) sbin/
2) share/
3) src/

Assuming you want to option 2 (/usr/local/share/ folder), type 2 Tab (2 key followed by the Tab key). And You will see this:

$ cd /usr/local/share/