Observable data lost on API call

so I am using Spartacus as the base of the project. In spartacus the data for the product is caught with this search method:

search(query: string | undefined, searchConfig?: SearchConfig): void {
if (query) {
this.store.dispatch(
new ProductActions.SearchProducts({
queryText: query,
searchConfig: searchConfig,
})
);
}
}


Now all of this is data is passed to the model$ Observable. In my project I have to implement show more which keeps the display of previous items and displays new items. When I call the function:

getPageItems(pageNumber: number): void {
this.routing
.getRouterState()
.subscribe((route) => {
const routeCriteria = this.getCriteriaFromRoute(
route.state.params,
route.state.queryParams
);
const criteria = {
...routeCriteria,
currentPage: pageNumber,
};
this.search(criteria);
})
.unsubscribe();
}


This updates the entire observable and I lose the previous product items. How can I keep track of the previous product items and push new product items?

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