How to set up Product Tour on app that loads in new tab?

Context: we already use Intercom Chat in-app and that works just fine.

I'm trying to create a Product Tour. To launch the builder, I enter the URL. We're a Shopify Sales Channel, so putting the URL in launches the Shopify login screen. I log in, navigate down to Sales Channels, and then click our app — all while staying in the iframe that Intercom pops up.

Here's where things break down.

When I click to launch our app, it always opens in a new tab. That new tab comes through on my full browser and not the iframe from Intercom. I can't replace the URL in the iframe to be my app. Shopify doesn't let me right-click and choose to open our app in the current tab.

I've checked that the app_id lines up between Intercom and our Product — it does.

So, I'm stuck. How can I "force" the Product Tour builder to load when I can't get access it via the iframe?

I appreciate any and all guidance here — thank you.