There isn't a way to create sub-pulses in monday.com right now, but we have some features that might fit what you're looking for!
We recommend using the Checklist feature within the updates area of each pulse! Utilizing the checklist will give you the low-level pulse detail that you are looking for when breaking down your tasks. You can add all of the relevant items as a checklist inside the pulse, and then you can then check those items off until everything is complete!
Alternatively, you could also think of each group as a checklist, using pulses beneath it to reflect lower task levels. This is very useful if your board functions as a personal weekly task list, because it will help you stay organized so you don't miss a step!
If you have any questions about this or anything else, feel free to reach out to our customer success team at firstname.lastname@example.org :) We're happy to help!