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.