.ott template files are intended to contain the collection of styles required by a document category (private letter, business letter, academic paper, novel, …) and initial “constant” text.
Therefore I doubt that any document in any category ever need 300 pages of shared text. You should reconsider what is common to your various files (title page skeleton; front material like copyright, publishing information, intellectual property; empty TOC, skeleton chapter with header and footer, empty alphabetical index, perhaps back material). All in all, this should amount to at most 20 pages depending on the sophistication of your layout; usually 10 pages is a maximum.
But if you’re in a mood to create a 300-page template, Writer won’t object and can perfectly manage it.
Saving a template and making it your default are two separate things. If you’re writing documents requiring several different templates, don’t one of them the default and select the appropriate one at creation time with File
>New
>Template
. Note this can always be done, no matter which template is the default.
To reset or change the default template, File
>Templates
>Manage Templates
I am not sure to have understood your procedure.
Ideally, always manage your templates from within Writer. Then, they will be stored in the directory where Writer expects to find them. Tools
>Options
, LO
>Paths
allows you to define additional user directories for templates so that they are not hidden inside “internal” directories and you can manage them easily with your file browser.
Don’t try to save “manually” as .ott. This effectively creates a bare template but some nice properties are not enabled. To manipulate/create templates, File
>Templates
>xxx
. The templates will be known to Writer and document auto-update when you modify a template becomes possible.
A template is a “universal” “neutral” model from which you derive a specific .odt document. Therefore Writer protects the template by not allowing overwrite and the template can be used for other new documents. Since the document created from the template is a new one, its name is Untitled1.odt by complete ignorance of your purpose.
It is not “confusing”. It is intended (and logical), once again to avoid overwrite of valuable files (a good template requires a lot of work).
PS: when asking here, always mention OS name, exact LO version (and save format).