This tip can be combined with any systems engineering methodology, not just the simplified Webel recipe for pragmatic SE with SysML.
The umbrella term functional analysis is rather over-loaded, and different terms are used in various formal SE methodologies. Here it means simply the identification of white-box Activities as usages (the 'behavior') in CallBehaviorActions in higher level black-box scenario Activities related to UseCases.
Webel recommends custom stereotyping the Activities that are identified as white-box (as opposed to black-box) as soon as possible. There are many candidates, just «whitebox» as a keyword is fine. Some formal SE methodologies already have a recommended stereotype for them, if you are using one of those, by all means use that. And, due to the wonders of SSoT, you can always change it later and it propagates throughout your SysML model. The main thing is that you do it all.
In the Webel approach to SysML modelling, we try to use more forgiving logical strategies, and not rely on ownership structure too much. Yes, you can group your white-box Activities under a Package hierarchy whitebox
the functional-analysis
or such, and then you could show the 'owner' of an Activity on a supporting Diagram (in SysMLv1 one can show an Activity symbol on a BDD), but that's not alone very flexible.
The Webel recipe for pragmatic SE with SysML use special terminology for «whitebox» logical drill-down: