Hi @Anuka,
Firstly, you are welcome. I'm glad that the plugin is helping people.
And I think RESCRIPt's edit taxonomy is the right answer here. It is better to edit taxonomy file first, and then use the plotting tool. Some regex knowledge is required to accomplish what you asked, and I'm not good at it. 
But I think the pattern is something like below:
^(k_)*(p_)* etc. etc. (s_)*$
Maybe @SoilRotifer could help us better.
Best wishes,
Kaan