Can not confirm. The Thumbnail view and the deletion button on each preview in the StartCenter does delete and individual document from the per-user cache held in the user's LibreOffice profile -- i.e. %APPDATA%\LibreOffice\4\user\registrymodifications.xcu

Deleting via the StartCenter thumbnail view also is deleting that entry from the MRU list on File -> Recent Documents which is again held and built from the per-user registrymodifications.xcu configuration file.

There has never been an ability to delete directly from the menu, just to clear the entire list--emptying all history out of the registrymodifications.xcu cache.

Testing Windows 10 Ent 64-bit en-US (1803) with
Version: 6.2.1.0.0+ (x64)
Build ID: dfa1f1f872c418e89757a3985979b79e94c12fcc
CPU threads: 8; OS: Windows 10.0; UI render: GL; VCL: win; 
Locale: en-US (en_US); UI-Language: en-US
Calc: CL

and also recent builds of master/6.3.0alpha
Version: 6.3.0.0.alpha0+ (x64)
Build ID: 2f1b939aeebf871a64fb587c078f87a5a0a9b137
CPU threads: 8; OS: Windows 10.0; UI render: default; VCL: win; 
TinderBox: Win-x86_64@42, Branch:master, Time: 2019-02-20_13:57:59
Locale: en-US (en_US); UI-Language: en-US
Calc: CL

While you may not be able to replicate bug, pls advise what action(s) I might take to rectify issue.  As stated in bug review request, files are also slower to load since this problem occurred.
Can I delete individual files from any other file etc within my system or can it only be carried out via registry modification?
Regards
Richard

The thumbnails and the MRU list item are stored in a XML text file--registrymodifications.xcu, located normally on Windows at C:\Users\<username>\AppData\Roaming\LibreOffice\4\user

You can use any text editor to delete the stanzas holding the stanza for each item.

<item oor:path="/org.openoffice.Office.Histories/Histories/org.openoffice.Office.Histories:HistoryInfo['PickList']/ItemList">

it will include a PNG thumbnail in (stored as base64) and the UNC path to the file.

Alternatively, you can clear out the recents from the LibreOffice registry from the main menu File -> Recent Documents -> Clear List

But you might review the thumbnails held in the registry, to see if any are exceedingly large.

Could you please try to reproduce it with the latest version of LibreOffice
from https://www.libreoffice.org/download/libreoffice-fresh/ ?
I have set the bug's status to 'NEEDINFO'. Please change it back to
'UNCONFIRMED' if the bug is still present in the latest version.

I continue to have issue with not being able to delete a single file from 'Recent Documents'(RD) and all files load relatively slowly from Recent Documents as compared to prior notification of bug. Bug continues with me using vers. 6.2.2.2.
I am able to delete all files from RD.  
I have changed number of files in RD using 'Expert Configuration' - file loading and deletion from RD is still same as when bug reported. 
I have deleted User from AppData/LibreOffice/4/User/ to no avail.
I am not aware that other products such as Microsoft Office have slow load times and generally my computer runs well and fast in all other applications.
I use auto update for Windows 10 so as far as I am aware my Windows has current patches/ updates etc.
I think that loading files Libre type files from Windows Explorer is faster than from RD.
Regards
Richard

Could you please paste the info from Help - about LibreOffice ?

Created attachment 150837 [details]
Libre Help About as requested

Further to my other comments I have observed that using the Calc spreadsheet that when i wish to insert a row it takes quite while for the dropdown window to appear when I place the mouse pointer on the Row icon on the toolbar.  I also observe that when I wish to edit a cell using F2 it seems more difficult to edit the cell on the command like rather than within the cell itself.

It seems to me there had been a significant 'slowdown' in the ability of LibreOffice to react to my mouse etc.  There is a significant delay in many of the functions within the programme that did not exist prior to my notification of the bug.  It is little like when I sometimes start up windows where a whole lot of programmes run at first which uses a lot of memory and disk access and then when the system has settled after say half a minute I am able to access any software very quickly.
Hope this is useful
Regards

Further to my other comments I have observed that using the Calc spreadsheet that when i wish to insert a row it takes quite while for the dropdown window to appear when I place the mouse pointer on the Row icon on the toolbar.  I also observe that when I wish to edit a cell using F2 it seems more difficult to edit the cell on the command line rather than within the cell itself.

It seems to me there had been a significant 'slowdown' in the ability of LibreOffice to react to my mouse etc.  There is a significant delay in many of the functions within the programme that did not exist prior to my notification of the bug.  It is a little like when I sometimes start up windows where a whole lot of programmes run at first which uses a lot of memory and disk access and then when the system has settled after say half a minute I am able to access any software very quickly.
Hope this is useful
Regards

Created attachment 150930 [details]
copy of deleted Libre programme

I have resolved this reported bug by deletion of the LibreOffice 6.2 Help Pack (English US ) from my system (see latest attachment dated 2019-04-22) .  I had installed this in Feb 2019 and in retrospect this ties up with my observing a bug with Libre. I had installed this programme to have help available when I use LibreOffice but I it did not appear to work and I did not immediately uninstall it.

Without trying to be obvious, this help programme has negatively affect the operation of LibreOffce for me and no doubt this programme either has a bug or bugs or it is not an appropriate one for the use I have for LibreOffice.

I would appreciate feedback on this issue pls.
Regards