In the Terminal Application on the Aquarius M10, is there a capability similar to Tab-Complete when using the on-screen virtual keyboard?
I think it's sufficient to tap on the terminal window to send a TAB.
You can swipe to the right on the console area and that will tab-complete. I assume it's sending a tab character.
Added to the "swiping right" you can also find a TAB key within the terminal. You have to hold the layout icon (orange area on the bottom left here: Terminal on Ubuntu Touch) and select SCR. You'll get a selection of keys with tab amongst them.
I am used to vi as command editor but Tab-complete works fine for me in the on-screen keyboard.
You have to switch to a different 'layout' as it is called in the keyboard/terminal settings. This is the white-on black ribbon above the keys and you can choose one with a TAB key by holding down the keypad symbol on the left side of the ribbbon and selecting "SCR".
Edit: I didn't know about the swipe or tap and that turns out to work just fine.