Having Trouble Setting up ModelDrivenFormIntegration control

[Cosmic_Kitchen]

I am new to embedding Canvas apps in a Model Driven form. I am trying to follow the instructions in this Microsoft Doc so that I can practice with form integrated canvas apps.

Pass the current record as data context with an embedded canvas app - Power Apps | Microsoft Docs

I don't know if I am hitting a glitch unique to the 90-day trial CDX environment I am using or if I am doing something wrong. Any help is appreciated.

The Table is OOB Case (incident) I am using the 'Case Title' field for the Canvas app control:

When I click 'Customize', it opens a new window (pop-up blocker IS disabled)... but it fails to load every single time and sits stuck on this screen indefinitely:

I am trying to embed a canvas app that will display a sub grid of Many-to-many relationship records, and include a combobox/dropdown to add more of those records to the sub grid. In order to display the current list of associated records, I am assuming the app needs to be connected directly to the record of the Model Driven App form... Am I going about this all wrong?

[Cosmic_Kitchen]

To elaborate a little on my practice project. I want to make 'Tags' for Case records. Tags are hosted in a custom lookup table called Case Tags. I want the embedded app to look like this:

Where a user can first see what tags the record has been given already, delete them if needed and add more from the ComboBox if needed.

I am assuming the Items property of the Gallery should be something involving ModelDrivenFormIntegration.Data.... but don't really know, just going to trial and error if I could even get the control 😅