for your first question, if you aer using Non-sequental Mode then you could find MEMs directly under the NS object list, The DLL version is used in sequential mode alone! Dd/}Ya(Gi
z\}!RBOq
For your 2nd Q, like the upstairs's reply, the STEP files should be saved under ZEMAX\Objects\CAD Files. 8~5|KO >F
Z{}+)Q*Q
Hope this would help :)