You are asking for pie graphs specifically which are good for one thing and one thing only: showing which part or which combination/coalition has a share of 50% or more. Most often, they should have just two segments or visually highlighted segment groups.
You currently want to show three data points at once, but your data set is ordered hierarchically:
- Participants whose gender we do not show.
- Participants whose gender we do not know.
- Participants whose gender we know but are not allowed to share.
- Participants whose gender is not covered by our data structure – some transsexuals, most intersexuals, corporations, groups, …
- Participants with disclosed classic gender.
- Participants who self-assign to the female gender – women.
- Participants who self-assign to the male gender – men.
You want to collapse the sub-points of the first bullet into one, but not of the latter. That is a categorical error!
You have three, maybe four choices of diagrams:
- Show the top tiers only.
- Show the reasons for not showing the gender.
- Show fe-/male proportions only.
- Combine the last two, i.e. show all lower tiers.
Those show very different things, not all of which are of actual interest. You obviously want the third one, or a combination of the first and the third one. That is possible, but not as linear segments within a single pie chart: You could put the 7% N/A either into an outer ring or into a center circle, probably painted grayish (or semi-transparent); the former works well with multiple pie charts shown next to each other because you get to see data and quality of data at once, the latter may be better stand-alone.
To finally answer your actual question, the correct label for each segment follows automatically from correctly labeled charts.