How to use pabot effectively

Hello All, We have 14 group of test cases and i would like to execute each group like below.

And I want to use only one pabot process not multiple and then merge, because in my case merge will take lot of time. happy to connect personally if any one want to help.group1 → parallel
group2 → sequential
group3 → parallel
group4 → sequential
group5 → parallel
group6 → sequential
group7 → parallel
group8 → sequential
group9 → parallel
group10 → sequential
group11 → parallel
group12 → sequential
group13 → parallel
group14 → sequential
group15 → parallel
group16 → sequential