I have a power app for leave requests for my business and wanted some advice on adding some items.

I want to add an attachment button to allow staff to upload medical certificates etc and for those to be stored in the SharePoint list of the power app, or be able to use power automate to send the attachment to HR.
I'm currently using the get manager function to send the approval however I want to mitigate the manager being away and have multiple approvers...what's the best way to achieve this?