Thanks for joining in on the thread, Davylinhardt.
With the new QuickBooks Online mobile app, you can already search using the terms associated to the invoices. You can also use the Sort or Filter options depending on the you're in.
For example, you're in the Invoices page. We can filter the invoices by status; Need attention, Overdue, Open, Paid, or All. Then, you can already search the terms in the Search field. You can use the terms such as invoice amounts, invoice numbers, description of an item, customer name, messages, attachment name, etc.
Make sure the app is always updated to ensure that it syncs your QBO data properly.
You might also want to see what other features are available on the mobile app. You can use this link for reference: Compare mobile app features.
Let us know uf you need anything else. Have a great day!