From where do you need this value list to work? What table occurrence (box in your relationship graph) is that layout or portal based on?
For a standard relationship based conditional value list (there are other types), that is a very important detail as it determines what to specify in the "include only related values starting from" part of the value list set up.
Looks like the conditional value list should be based on the relationship form Meetings to Stakeholders. It's hard to tell from your graph but the table occurrence for Meetings that you need doesn't appear to be on your screen shot. There should be a relationship from Projects to ProjectsStakeholders to Stakeholders. This relationship would be used to add Stakeholders to Projects as stated at the beginning of your post and would be the relationship needed to show Stakeholders for a Meeting about a particular Project. Hope I got that right and makes sense. Had to use a pencil and piece of paper to figure it out. Would be easier in person lol. Good luck.