Remove Individual "Recently Added" Movie(s) from Home view on Synology DS918+ - The Definitive Guide
I found this to be a piece of cake to do.
After getting hints from here and various other places in the forums this is what I did. I have Plex running on my Synology NAS 918+. Initially, I had no access to the Plex folder until I added Read/Write permissions for my Username in the Synology Control Panel. But you won't need to do this if you already have access to the Plex server folder on your NAS or PC/Mac.
Here is the process I went through. Bear in mind this is for the Plex Server running on a NAS so you may need to adjust or miss some steps to suit your setup.
Open the Control Panel>Shared Folders> Select Plex folder in the list, then select Edit>Permissions. Tick (Check) "Read/Write" for your name and click OK to apply the changes.
Open the Synology Package Center and stop Plex running using the Action menu. On a PC or Mac, I believe you would just quit the application to stop it running.
Open Filestation on the NAS and copy the current Database from /Plex/Library/Application Support/Plex Media Server/Plug-in Support/Databases to a separate folder on your NAS. I used my Shared Documents folder. The Plex database file is "com.plexapp.plugins.library.db". You should also copy over the 2 files ending in .db-shm and .db-wal if they exist in the Database folder. Then delete the "com.plexapp.plugins.library.db-shm" and "com.plexapp.plugins.library.db-wal" files that are still in your Plex Media server Databases folder, but do not delete the "com.plexapp.plugins.library.db" file. For safety in case of errors, you will be working on the copy of the Database file you just made which you will use to overwrite the existing one when all your changes are made. The copy you made in your NAS Documents folder (or elsewhere) should remain as an original file backup until you are happy that the changes have taken place as expected.
Now copy the Database copy you made, from your NAS Documents folder (or wherever you saved it) to your PC or Mac's Documents folder. This will be the file we will work on.
I then downloaded and installed the "DB Browser for SQ Lite" app from here: sqlitebrowser.org/. Windows and Mac versions are available.
Open the Database in the "DB Browser" app that you saved to your PC or Mac. Navigate to the Browse Data tab and using the Table selection menu list at the top of the app select the "metadata_items" section.
Using the Plex web app, locate the Movie you wish to remove from the "Recently Added" view. In my case, this was a copy of an old movie I had just added but didn't want it to appear in "Recently Added" as it was a few year's old. Hover over the Movie poster and make a note of the ID number that appears at the foot of the browser window whilst over the poster at the end of the long piece of text and preceded by "key=/library/metadata/" which in my example was "key=/library/metadata/10959" so the iD number I needed was 10959.
7a: Useful Notes:
You can also hover over any Movie in your lists and the same information will appear at the foot of the browser so you can identify the Movie's location in your Database.
Also by examining the content of the "title" and/or "title_sort" fields in the DB Browser app I was able to ascertain the location of other titles in my Database such as "TV Series" for even more editing options. The world is your oyster with even a very basic knowledge of Database editing as this app makes it so easy and as long as you only work on a copy and not the original file you can always revert back should you come up with any issues.
Go back to the DB Browser app and enter the ID number into the ID Field "Filter" box at the top of the app view. The required data for the Movie in question should appear on the line below.
Navigate to the "added_at" field data and select the Data box:
Using the "Edit Database Cell" box on the right of the app window, change the existing date and/or time shown to one in the past. In my example, the existing data was "2018-02-09 15:23:06" which I just edited the year to 2017 to put it in the past which would remove it from the "Recently Added" view. So my edited field data read "2017-02-09 15:23:06":
Click "Apply" below the text box to apply the change.
Repeat steps 7 to 11 for any further titles you wish to remove, remembering to apply the changes after each edit. It is also very simple to edit other data fields such as "studio" (Movie Studio), "content_rating" (Certificate such as GB/12 or PG-13 for the USA) or "year" (Year of release) as examples. It's easy to figure out the Data Row headings in each field by examining the existing data they contain.
After making all the changes you require you must click on the "Write Changes" at the top of the app to save all the changes you made to the Database file.
Finally, check that the Plex Server is still not running on your NAS (or PC/Mac) and copy the newly edited Database back into the Plex Server Database folder overwriting the existing one if prompted. Copy back to /Plex/Library/Application Support/Plex Media Server/Plug-in Support/Databases folder overwriting the existing file "com.plexapp.plugins.library.db".
Restart the Plex Server on the NAS or PC/Mac and you should find that the edited titles no longer appear in the "Recent Added" section. In case of any errors encountered use the backed up "com.plexapp.plugins.library.db" file from step 3 to revert back to the original file.
Here's hoping the above helps someone out!
Update: After updating the Plex server to the latest version on my NAS, it removed my permissions. I just re-enabled them and all is well again. Not a dealbreaker, just something I need to remember to do after an update.