Do nothing. Seriously. Allow yourself to become bored and you'll find your brain has suddenly got time to work on all the problems you mentally shelved. There's a good reason why a good number of ideas happen in the shower.
My mental model is that any point the brain is dividing its resources between execution of current events and processing old events. If it spends too much time processing old events then it has no resources over to properly execute in the now.
When this happens some people just drop the unprocessed tasks from the queue to free up resources while others (like me and you) starts experiencing immense stress forcing us to drop what we are currently doing instead.
One way is not the other, sometimes I wish that I could execute better in the now but sometimes others wish that their brains didn't automatically drop important experiences without properly processing them first.
How to fix this? One way is ADD medication, increasing your dopamine forces your brain to focus on the now and drop old packets. It helps me execute better but I definitely become less creative and have a harder time remembering what I did when I took them. I might feel more creative when I'm on them, but most of those thoughts will be gone without a trace since they weren't properly processed.
Then decide how many of these actually need to be done and when, and organize your next week/month based on this.
I distinctly remember one time I was sitting there, mind aimlessly wandering when the solution to a bug I was having in my code on Friday popped into my head. I wanted to go straight into work to fix it!