Add or Remove Folders from This PC in Windows 10  

You could hide the folders if you like.

Set or Unset Hidden Attribute of Files and Folders in Windows 10

all these folders are hidden with one exception:
when I try to export bookmarks from the browser,
the folder "documents" is shown,
can this be removed?

patrickdrd said:

all these folders are hidden with one exception:
when I try to export bookmarks from the browser,
the folder "documents" is shown,
can this be removed?

That folder is probably being used by the browser, and why it's showing.

If you like, post a screenshot showing this to see if anything may stand out.

It looks like you uploaded the image, but just didn't attach it in your post. Now fixed.

Does hiding the Documents folder from within this dialog box keep it hidden for you?

Is "Show all folders" turned on in this dialog box?

You should be able to set it to hide using option 4 below from the dialog.

Set or Unset Hidden Attribute of Files and Folders in Windows 10

You can check using option 1 below to verify if "Show all folders" is turned off for the navigation pane from the dialog.

Turn On or Off Show all folders in Windows 10 Navigation Pane