TemperMonkey works, but...

It's UI is very unintuitive but I still kept using it for many months daily, it did its job. However, then I encountered a deal-breaking bug, it seems:

Bug: I have two scripts applied to a base URL. After navigating the portal for a while, I ended up with TemperMonkey reporting it applies about 70 scripts. And it apparently did, because loading the pages within the portal became pretty slow.
I then migrated to FireMonkey, which has much more intuitive UI and doesn't exhibit this bug.