VurRouter transitions on more than one router - vuejs3

Question

I prepared a boiled-down example on stackblitz:
https://stackblitz.com/edit/quasarframework-vy4eiw?file=README.md
The problem I try to resolve is this:
A quasar 2 app build with vite and vue 3 (and GSAP) uses layouts
Currently there are 2 layouts: StartpageLayout for the startpage at route ´/´and MainpageLayout for all the other pages at route ´/main´ and any children of it (/main/:child´`)
The MainpageLayout also contains the navigation menu
The navigation menu should be created (later on with an animation) when any route starting with ´/main´ is hit and destroyed, when there is a change to any other route
While navigating through any ´/main[/:child]´ route, the nav menu shall remain "stable" (not rebuild or anything like that)
The app uses 2 router-views for this, one in App.vue, one in MainLayout.vue. Changes between those states should mainly be handled in onBeforeRouteLeave and onBeforeRouteUpdate
To check, whether the app is in a "layout context", the routes have a meta.layoutKey, which is used in router guards to check, whether sth changed or not:
// Example: src/layouts/MainLayout.vue
onBeforeRouteUpdate((to, from, next) => {
console.log('%cMAIN_LAYOUT: onBeforeRouteUpdate invoked', consColRouter);
// compare meta.layoutKeys of routes
if (from.meta.layoutKey !== to.meta.layoutKey) {
console.warn(' YES, invoke router guard onBeforeRouteUpdate - animate!');
next() // this would be actually be called form an onComplete animation callback
} else {
console.log(' NOPE, do not invoke router guard onBeforeRouteUpdate');
next() // invoked as written
}
})
A pinia store manages state that (should) remember(s) activateMenu:
// Pinia store "pageTransitions.js" (composition API)
import { ref, reactive, computed } from 'vue'
import { defineStore } from 'pinia'
export const usePageTransitionsStore = defineStore('pageTransitions', () => {
// Pinia state in composition API
const pageTransitions = ref({
parent: false,
activateMenu: false
})
const setPageTransitions = (level, bool) => {
switch(level) {
case 'parent': {
pageTransitions.value.parent = bool
break
}
default: { console.log('default... must never happen!'); }
}
}
const setActivateMenu = (bool) => {
pageTransitions.value.activateMenu = bool
}
return {
pageTransitions,
setPageTransitions,
setActivateMenu
}
})
If store.pageTransitions.activateMenu is true, show the menu, if false, remove it. It is imported in MainLayout in order to use the activateMenu constant to manage the state of the nav menu. The onMount method sets this store variable to true. And it should be set to false in a ònBeforeRouteLeave`... (not yet implemented)
While the change from the startpage at ´/´to the MainPage at ´/main´ and vice versa works fine (even with animation, due to the store variable store.pageTransitions.parent), I keep having troubles with changes from ´/main´ to any child route ´/main/:child´ and vice versa. E.g. when the app is at /main and the user clicks on ´items 101´, the whole MainLayout is reloaded - also App.vue runs through its onAppear hooks again (see console) – and the nav is set to false again.
The goal is to not influence the MainLayout not its nested nav menu at all.
I wonder, why those reloads happen? MainLayout's onBeforeRoute checks against meta.layoutKey which does not change. But then I also observe that the pinia store gets loaded again, and the actiavteMenu var is set up false again...
Does anybody see my error(s)?