Windows 10.
That "devices" folder is empty, even if a device is connected. (I have 3 devices in all)
What filename (or extension) would it be, anyway?
Where is this "transfer all" you suggest?
Somewhere in the Connect page?
On the device?
I know, you're not supposed to make a mistake in the first place, but it ought to be easier to recover from it!
Transfer All, or its equivalent will be on the device itself. I think it's under History, but it's under wherever you get to look at your activities on the device. Step through the menus and have a look for yourself. You'll soon see something that is suggestive of being able to transfer everything. Might be Force Transfer. It's such a long time ago.
As for having files on a computer. When the FR305 came out GC was very rudimentary and we all used GARMIN Training Centre on our computers. Now we have GC on the interweb. If you're happy devolving everything to the interweb, all well and good. Personally, I like to keep my recorded activities somewhere under my control. Until recently, most devices automatically kept copies of recorded activities on a computer. Think of it as a form of backup. Now, with the 920, I run a script every time I charge my 920 to remove the activities and save them somewhere safe as well as having them uploaded to the GC.
You might find something useful in the manual - http://static.garmin.com/pumac/984_OwnersManual.pdf
I deleted an activity on my vivo active today and I want too retrieve it and upload it
I deleted an activity on my vivo active today and I want too retrieve it and upload it
If you really deleted it directly on the device, then the activity is lost (unless you back up regularly the activity files, but I assume in such case you would not be asking how to retrieve it). If you deleted it in Garmin Connect (Mobile or Web), then the activity file is still in the folder //GARMIN/Activity/ on your device, and you can copy it to your computer over the USB cable and import it to Garmin Connect.
I am on a Mac and iPad I lost my ride today because I deleted it by mistake is there any way to get it back on my Garmin 520
If you deleted it just from Garmin Connect, you can recover the FIT file over USB, directly on the device in the folder //GARMIN/Activity. If you deleted it from the device, you can try the tip from this thread: https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/223552/deleted-ride-by-mistake/1053830#1053830
I would like to download my recently deleted workout
Assuming you meant activity, as that is the subject of this thread. Which Garmin device do you own? If it's new enough to be able to connect a USB cable to it and to your computer and see the drive associated with your device, then see trux's advice above, or my answer to a previous post here: how do I get my activity back if I delete it?