Other than the Satipatthana Sutta (where you quoted), I could not find a discussion on those. I think they mean the following:
Nirāmisa dukkha:
Sometimes, a Noble Disciple may be discouraged by being unable to advance “fast enough” on the Path. One thinks about “why am I not getting to the Sotapanna, Sakadagami, Anagami, or Arahant stage (depending on one’s level)?” or “Is there anything that I am missing to make progress?”, etc.
Nirāmisa adukkhamasukha:
The absence of either nirāmisa sukha or nirāmisa dukkha, i.e., a neutral mindset.