In Constellation, I would not recommend replicating the old Cosmos custom control pattern directly. Since Constellation behaves more like a SPA, the better approach is to load the Pendo script once at the portal/shell level and then trigger Pendo refresh logic whenever the active assignment/view changes.
If standard portal-level JavaScript is not sufficient for your use case, the cleaner Constellation pattern would be a custom DX component or supported extension that hooks into the view lifecycle and invokes the Pendo API on assignment/view navigation. That is generally more upgrade-safe than injecting JavaScript into each individual view.