LR6 does take advantage of the extra memory. I added the new memory and now have 32GB of RAM in my iMac. I had some batches of JPGs to import. During the import process - and the generation of previews - LR uses more and more memory. Interestingly, once the import is done, it doesn't release the memory. On the next import, it grabs _more_ memory. By the time I had finished importing nine batches of 40 photos each, LR 6 was using 26 GB of memory (per the activity monitor)! I could just watch it growing and growing. Nothing else was running, and with 32 GB of hardware RAM, no memory was compressed and swap was 0. Going into develop and viewing one of the imported photos didn't release any memory. Exiting LR6 did release all the memory. My guess is that since the memory was available, LR 6 wasn't bothering doing any memory management. If I had another large process asking for memory, then I expect LR 6 would release some memory, but I haven't tested that. Very interesting - I assume this is intended behavior and not a bug. I have never looked at memory usage for LR before.
David