First, I have no connection with this great app, but have used it enough to learn some tips, so, responding to the last three posts in the hopes that this might help but know that I can't do anything.
In addition, over the years (BM, "Before Mice") learning key combos have served me well with this and other keyboards.
>> Width Setting <<
Usta be that you got to the keyboard settings via settings/Language&Input/..., but that path seems to have disappeared with android 8.
You now have to get to Hackers Keyboard's settings using <tab-hold> (took me a while to find it)
Once there, the first two settings are keyboard height, one for portrait, one for landscape.
>> Home, etc keys <<
Tap the <Fn> key to get to all of these... pita perhaps due to extra taps, but screen real estate is extremely limited. fwiw, the <Fn> key seems to have become a standard throughout all keyboard mfg's that don't include a full key set.
>> SwipeSelection <<
It's interesting to note that, afaik, no android keyboard apps have this option. Google offered left/right cursor movement by swiping the <spacebar> a couple of years back, but that seems to be gone as well, probably because <spacebar/hold> now brings up keyboard selection.
_However_ some apps (notably Google apps) seem to have recognized the need and applied their own variant... <tap/hold> at the beginning of a selection segment, then drag to the end of the segment.
Not sure what you mean by "up/down" selection, but this also works for that.
fwiw, I tried this on another, non google app, and it didn't work, so don't know how widely available drag selection is.
Hope that this information is useful,
Beverly Howard