From what I understood from your description is you want to loop over the fields of sldvData struct. And for every iteration you want the current and next field of the sldvData.
fields = fieldnames(sldvData);
for i=1:2:numel(sldvData)
var1 = sldvData.fields{i}; %gives slPath, sfObjNum and designSid
if i+1 <= numel(sldvData)
var2 = sldvData.fields{i+1}; %gives other two
end
end
