P: Allow Mobile Downloads.lrdata to be moved to another location

No, but in Preferences > Lightroom Sync you can set a normal folder location so nothing goes into Mobile Downloads.

In an earlier post I asked about moving a file, I identified the wrong one by mistake. I meant to ask can you move 'Pictures/Lightroom/Mobile Downloads.lrdata' to an external disk?

I'm extremely pleased that Adobe has implemented this capability. I had stopped using Lr Mobile to send my iPhone photos to Lr because I didn't want my boot drive filling up, and moving them manually was too much of a hassle. Very happy to dump my interim solution and fully us Lr Mobile. Of course, I now discover that it only syncs while the app is running and phone unlocked - no background syncing. Arrrggghh!

Michael - I can't see any reason not to have photos from Lr Mobile go into your default photo folder. I use a simple structure of YYYY/MM for my photos. (Yes, I know folder structure shouldn't matter in Lr - use keywords, collections, etc....which I do; however, I don't want a single "photo" folder to grow to 100k files one day - that's unwieldy for many reasons.) Anyway, I'm now saving my Lr Mobile photos to photos/year/month and it seems to be working just fine. I auto add them to a collection on my phone called "Charles iPhone" and I use that collection on my desktop to do my culling, tagging, and moving to other collections. This has basically covered the two parts of the normal import process that I need: moving the photos into my folder structure (automatic with Lr Mobile) and putting my new photos in a collection to review . Of course, this all very new, but seems to be working well so far.

Cheers

So we can now place imported ipad/iphone photos in whatever directory we want. This is great. 

Is there a workflow reason not to just have them dropped in whatever your default storage folder is for photos? It also seems that since we can sequester them based upon date that this change removes the necessity of ever syncing your ipad/iphone directly to your computer for offload and storage of images, which is nice.

Though I did notice that when new pics are brought in, they're accompanied by an "info" file that tells you what device took the image.

I saw that the other day. Finally! I was very happy to see this implemented.

LR CC 2015.4 / 6.4 implements this: "Customers can now set the location of where photos are stored when downloaded from Lightroom mobile or Lightroom web in the preference panel or contextually in the folder panel".

I also have problems with this. I wonder if storing in the Creative Cloud would work better than Dropbox or Google Drive...

I know this is unrelated, but what I really want is to use a fast Lightroom that had storage for all my photos and settings in a secure cloud. Not to mention, better collaboration tools. I find sharing those albums with someone else using Lightroom to be practically useless...ok, off my soapbox (before it starts getting too bloated)

Ok, now that I deinstalled the whole Creative Cloud and removed everything like presets, preferences and installed CC again it's working fine and the size of the MobileDownloads.lrdata is decreasing when I move photos to another drive, as it should be. I think it was a problem with my two machine system where I syncrd my catalog and previews over a network drive and my presets and prefs over Dropbox. Both Macs where connected to LR mobile. I think that was the confusing part where something went wrong. It's sad that the catalog is not working on network drives.
I guess I have to rethink my workflow and use only one computer to do my post work.

But this problem also was in 2015.1.1. I will try it on my MacPro tomorrow from where I copied the catalog over.

Forget about using LR 2015.2 aka LR 6.2 or 6.2.1. It is nothing but problems form the interface change to compatibility with the new Mac OS 10.11 El Capitan.
Simply roll back to the previous version 2015.1 aka 6.1 and keep getting meaningful work done, and stop being Adobe's Guinea Pigs.
https://helpx.adobe.com/lightroom/kb/...