Easiest way to get reminders to follow up on emails with no response? (Outlook for Mac)

I want to get a notification or, ideally, have the email return to the top of my inbox if an email I sent hasn't received a reply by X time. I'm on Outlook for Mac (16.62, toggled to New Outlook). My workplace has disabled me from adding add-ons, and an email request to IT has gotten me nowhere.

I don't think I can get exactly what I want without an add-in, but barring that, what would be the most efficient way to get some kind of reminder or notification to an email in which the recipient hasn't replied by the scheduled reminder time? (Or is there any workaround to get an add-on installed?)

So far, I am flagging every email I send, and then it shows up in To Do, where I can set a reminder or due date. But To Do doesn't know or show whether I've gotten a response or not, it just reminds me to go back into Outlook and check, which is more steps than I'm interested in. Or I can go to my Sent mail in Outlook and filter for flags, but New Outlook doesn't allow flags to be linked to deadlines. (In general I like New Outlook and don't want to switch back.)

Any ideas?