First, print feature is based on office products such as word, excel,PowerPoint and so on, and has little to do with SharePoint.
So there is no related SharePoint solution to add a message when printing a document.
In my tests, I couldn't reproduce your problem. After I set the configuration, SharePoint will automatically retain my settings and will not revert back to their default values.
You can run the below powershell command as an admin to define library settings.
$SiteURL = "https://tenant.sharepoint.com/sites/sitename"
$LibraryName = &...
I am assuming that you are changing all of the above settings with a SPO Admin account, or at least an account that has Owner permissions.
You could try changing the settings by utilising a PowerShell Script, an example of which you can find here
But, since you have seen some strange behaviour in your tenant, best you can do is open a ticket with MS. ...
You can break permissions inheritance and grant excusive permissions on folders as well in SharePoint online.
Follow below steps:
Go to document library
Click on ellipsis (...) - three dots next to folder name & select Manage access
It will open a panel at right side of screen. Scroll to the bottom of panel & click on Advanced link
It will open ...
You can get the recycle bin items based on Original Location like below:
Get-PnPRecycleBinItem | ? DirName -Like '*/mylib'
Use DirName column for Original Location.
Get-PnPRecycleBinItem | ? DirName -Like '*/Lists/Test_List’
You want to be creating an SpFx extension. Specifically you will want to create what is called a List View Command Set. Your best starting points (other than google) are these two GitHub repos:
Getting Started - Building Your First SpFx Extension
You would need to store the file hash as a column for each document
Before you save the file you could check if the hash exists.
A hash is a unique identifier based on the contents of the file
Try PowerShell command Get-FileHash