Exporting a JPEG copies all files in the folder

Try resetting the preferences.

https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/

A workaround is to edit in LR, then command to edit in Photoshop and Save a Copy... JPEG.  That saves only the one photo I want to save.

The new files were entered into the active Lightroom Library window.  The first photo of the day is IMG_4863.  The file I was editing is IMG_4869.  I wanted to name the new file IMG_4869 brown pelican.  The first new file was in fact named IMG_4869 brown pelican, but it was a copy of IMG_4863 and appears in the library right after IMG_4863.  The next file is named IMG_4869_brown pelican-2, is a copy of IMG_4864, and appears right after IMG_4864 as I right arrow through the library.

I tried making a new folder to export into.  When I tried to export one photo it tried to export 291, the number of photos in the original folder.  I tried to open both the JPEG and the CR3 in Windows Photo and neither one had the edits.

I verified that only the one photo was selected.  It still copied them all.  Right clicking and choosing Export has the same effect.  In fact, it tried to overwrite the three files it had copied the last time before I stopped it.

Jim Hess-I believe when I edit one photo it deselects all the rest, but maybe that is the problem

GoldingD-Here is the system info

Lightroom Classic version: 10.4 [ 202108071231-af9219b9 ]
License: Creative Cloud
Language setting: en
Operating system: Windows 10 - Home Premium Edition
Version: 10.0.19043
Application architecture: x64
System architecture: x64
Logical processor count: 8
Processor speed: 1.9GHz
SqLite Version: 3.34.0
Built-in memory: 7981.7 MB
Real memory available to Lightroom: 7981.7 MB
Real memory used by Lightroom: 1001.4 MB (12.5%)
Virtual memory used by Lightroom: 928.9 MB
GDI objects count: 735
USER objects count: 3066
Process handles count: 2643
Memory cache size: 44.6MB
Internal Camera Raw version: 13.4 [ 872 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2,AVX,AVX2
Camera Raw virtual memory: 5MB / 3990MB (0%)
Camera Raw real memory: 6MB / 7981MB (0%)
System DPI setting: 120 DPI
Desktop composition enabled: Yes
Displays: 1) 1920x1080
Input types: Multitouch: Yes, Integrated touch: Yes, Integrated pen: Yes, External touch: No, External pen: No, Keyboard: Yes

Graphics Processor Info:
DirectX: Intel(R) UHD Graphics 620 (27.20.100.8478)

Application folder: C:\Program Files\Adobe\Adobe Lightroom Classic
Library Path: C:\Users\rmill\Pictures\Lightroom\Lightroom Catalog-v10.lrcat
Settings Folder: C:\Users\rmill\AppData\Roaming\Adobe\Lightroom

Installed Plugins:
1) AdobeStock
2) Facebook
3) Flickr
4) Nikon Tether Plugin

Config.lua flags: None

Adapter #1: Vendor : 8086
Device : 3ea0
Subsystem : 85e6103c
Revision : 0
Video Memory : 128
Adapter #2: Vendor : 1414
Device : 8c
Subsystem : 0
Revision : 0
Video Memory : 0
AudioDeviceIOBlockSize: 1024
AudioDeviceName: Speaker / Headphone (Realtek(R) Audio)
AudioDeviceNumberOfChannels: 2
AudioDeviceSampleRate: 48000
Build: LR5x26

I would like to export an edited copy, so I Export from the File menu.  

Does this behave differently if you right click on the image and select export? .

/note/ above edited after having a duhhh moment/

Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.

/edit/ info that was included below as example, deleted to save space as OP has accomplished the requesr

You indicated that at one point you selected all photos. It would seem that you failed to change the selection from all photos to a single photo, and that is why the export included all images. That is the way I'm interpreting your workflow.