If you Install the Dataview plugin and enable Javascript queries, the following script will show all links pointing toward non-existing files.
I found this snippet on this forum, but I cannot remember where or who wrote it.
let d = {}
function process(k, v) {
Object.keys(v).forEach(function (x) {
x = dv.fileLink(x);
if (d[x]==undefined) { d[x] = []; }
d[x].push(dv.fileLink(k));
});
}
Object.entries(dv.app.metadataCache.unresolvedLinks)
.filter(([k,v])=>Object.keys(v).length)
.forEach(([k,v]) => process(k, v));
dv.table(["Non existing notes", "Linked from"],
Object.entries(d).map(([k,v])=> [k, v.join(" • ")]))
Also, a plugin called Find Unlinked Files can find unresolved links and create a note with links to click and create them when needed.