Indigo does support sending keystrokes directly to the connected host or server in the Direct Terminal Mode.
This may be required for hosts that require interactive keyboard input or those that use an emulation protocol such as VT100.
To swich to Direct Terminal Mode, with a session open and connected, use the main menu to select "Session > Direct Terminal Mode"
Now while in Direct Terminal Mode you must place the cursor directly in the data window to be able to send unbuffered keystrokes to the host.
With the cursor in the data window, you should be able to simply type characters/keystrokes and they should be send directly to the connected session.
(This should behave exaclty as it does in HyperTerminal)
There are certain CTRL keystroke commands that Indigo reserves for program shortcuts such as "CTRL-C" for COPY, so if you are not seeing the keystroke you type being sent to the connected session, you can try using the options in the Session > Transmit Control Code menu. These CTRL keystrokes can also be achived by including the SHIFT button in the keystroke: to send "CTRL-C" press "CTRL-SHIFT-C" in Indigo.