I recently updated LibreOffice to v6.1.3.2 on openSUSE 15.1. One thing
I've noticed is my own templates are now mixed in with the provided
templates. Why was this done? I now have to sort through several
templates, that I have no use for, to find the ones I created.
I make a habit of using the LibreOffice versions from www.libreoffice.org rather than from my operating system. i have found over the years that O/S versions have some bugs that LO versions do not. This may be the case here.
More importantly, I also use the Manage Templates options. This gives me two drop down lists in which to restrict which templates are displayed. The first contains a list of applications. The second one contains a list of categories which includes My Templates. All of my templates are Documents, so I select this it. Under Categories, I select My Templates. When I view the templates displayed, only one of them is not my personal created templates: Standard. So, I do not get the same results as you have.
You might also be able to move the undesirable templates to other categories.
Dan
File → Templates → Manage Templates → Filter: My Templates
That's where I'm seeing my templates mixed in with the provided templates.
Never mind. Found it.