In case anyone is interested, I think I've managed to achieve what I wanted to do, i.e. show the first row of launcher icons on the homescreen all of the time (like what pops up after unlocking or touching the homescreen).

In /usr/share/lipstick-jolla-home-qt5/layers/EdgeLayer.qml, change:
from
PauseAnimation { id: hintPauseAnimation; duration: 2000 }
to
PauseAnimation { id: hintPauseAnimation; duration: 2000; loops: Animation.Infinite }

In /usr/share/lipstick-jolla-home-qt5/main.qml, change:
from
} else if (switcher.count == 0
&& Lipstick.compositor.previousWindow == Lipstick.compositor.lockScreenLayer.window) {
to
} else if (Lipstick.compositor.previousWindow == Lipstick.compositor.lockScreenLayer.window ||
Lipstick.compositor.previousWindow == Lipstick.compositor.eventsLayer.window ||
Lipstick.compositor.previousWindow == Lipstick.compositor.powerKeyLayer.window ||
Lipstick.compositor.previousWindow == Lipstick.compositor.launcherLayer.window ||
Lipstick.compositor.previousWindow == Lipstick.compositor.appLayer.window) {

In /usr/share/lipstick-jolla-home-qt5/compositor.qml, change:
from
onAboutToShowWindow: {
root.showApplicationOverLockscreen = Desktop.startupWizardRunning
to
onAboutToShowWindow: {
root.launcherHinting = false
root.showApplicationOverLockscreen = Desktop.startupWizardRunning

then do:
systemctl --user restart lipstick

It's probably not the best way of doing it, and it's taken me absolutely ages, but it'll do for me.

Looks great! The second block of code is in main.qml thought.

There should be a way to prevent homescreen zooming out, like in this patch.

Thanks, fravaccaro - I've fixed the mistake above.
And I'd been wanting to get rid of that zooming but didn't know how to - until now!