hi,
Most people, like myself until 20 minutes ago, have no idea and experience of using extensions in Libreoffice Writer.
The reasons for this are simple: trust. Most people don’t trust extensions when it comes to important document editing work.
As a matter of fact, when I got to that extension page, it was enough for me to see “latest release 5 years ago”. I was gone. I mean, almost. Then, lower in that page, it turns out that there was an update even 6 days ago. Better!
integration
Installing it (speaking of Linux, forget the commercial OSs) goes very cleanly: you have to select it from a directory, where you saved it when downloading it.
Then you select the file and click okay, and ding, you have installed it. But this is when you expect the bad part. I mean, how on Earth will you ever find this new utility whatsoever?
Well, surprise! In the main menu!!!
File / Templates… and there you go.
Instead of
- “Manage Templates” and
- “Save as Template”,
now you have 4 +1 menu item. In perfect functional order, in two groups, the “manage templates” being at the bottom, as the 2nd group. Perfect!
- Edit Template
- Change Template (current document)
- Change Template (directory)
- Save as Template
– - Manage Templates
That’s what I call integration!!!
what happens if you uinstall it?
NOTHING bad! 
What you do with your documents template-wise are clean operations,
if you uninstall TCH you won’t lose any change.
good news:
There’s already a request to get this extension incorporated in the official releases.
The way to go!
This extension is soooo perfectly integrated in Writer that you have to keep in mind that this is an extension which you’ll have to install separately on a new machine.
available reviews
Well, some people are impressed with it, others don’t seem to get it work.
But people are very different, and their (our) situations are very different, too.
If someone knows what to want from Template Changer, like myself, they will find it very intuitive, and very accurate. And clean. I really am amazed.
As a matter of fact, I can easily “detach” a template from a document manually, and it works great, accurate and clean. So I didn’t really need Template Changer. But I tried it and now I’m so impressed that I’m trying to spread the word here 
what to use it for?
You need it. We all need it, cause LIbreoffice Writer has grown (evolved) in such peculiar way that besides being amazing, modern and logical, it inherited some ugly spots in its concept.
Templates are an ugly spot in the Writer concept 
You can easily bump into the problem of needing to get your document detached from a template. Or needing to replace the template with another one.
- you have created a new template from a document which was based on a template, and now when that old template changes, your new template will update, and then all your documents based on it will follow. Disaster
- You have created a Master Document Template, but it is based on a template, which you don’t want, because of the the above scenario.
- You would like to change the template which your document is based on… You could, of course, simple edit the template to get the desired changes in all documents…
BUT you like this template and want to use it in the future too.
Plus, there are other templates which sure work well.
You can achieve all these, and more 
Template changer is a very-very good functionality! Works very cleanly.
Template Changer is a great solution to a very old, inherited problem.
Basically, any reform regarding the workflow with templates should start with incorporating Template Changer in Writer. Moreover, once you have TCH, most of the problems regarding templates will be gone, and we’ll find ourselves on a new level,
when templates are no longer pre-made, pre-cut patterns, but STYLE Collections!
Let’s cross fingers, maybe it will be part of version 28 already!!
How old is it already? More than six years old…
No, not Libreoffice developers are slow… but users…
I have been told about 100 times by Ajlittoz, for example to check Template Changer…
and I only did it today
I mean, years later…
So, let’s hope that it gets adopted in Writer all the soonest.
Thanks and congratulations for creating and developing it !!
and for Ajlittoz for propagating it! 
Peter