Yes, I have had issues with this sort of thing, independent of my mood state at the time. I don't think it necessarily means you're manic or anything like that, since I've had it also when stable or depressed. I think it's a feature of bp1. The more I get to stability and reduce my anxiety, the easier it is to manage.

Suggestions: talk to yourself. Pick the tasks you want to focus on, and while you're super focused on that singer, remind yourself periodically about the cookies. Or use technology: set an alarm or timer so you don't have to worry. Don't beat yourself up about not focusing/being mindful - this is most likely a brain chemistry thing which is out of your control.

Try fish oil, it actually does help. Leave yourself notes and reminders. Set alarms for when you need to do something or remember something. And be kind to yourself - this isn't a "failing" of your mindfulness, it's a symptom of your disease.