too my understanding battle master lets them see and move people in gnw and dont know bout skill expert.

No. A leader and a senior could make everything the lower grades do.

In my group, we only have 2 Seniors and 4 Summon Masters .. So the only people can move members in lands during GNWs is limited, we encountered one time where we already placed and team-up our members in their respective lands and then the last 10 minutes, someone drag and drop randomly the members .. To avoid that, we removed Battle Commanders ..

Leaders and Seniors can do everything in the Group, just like what Shryke said above .. The only difference between Leader and Seniors is the ability to Distribute GNW Packs which is also the ability of the position called Quartermaster, this position is used if your leader is somehow, a busy person so that if he cannot log-in during Saturday GNWs, someone can still distribute the packs .. Summon Masters ability can only Set the Group's Capture Summon and Feed the Summon with Chakra. But with the Skill Expert, i guess the only thing he can do is upgrade the Skill Research Level, nothing more nothing less ..

Leader- yes, he can do everything. Seniors can't distribute packs, which quartermaster rank allows to do.