The Normal.pmvx document template is the default template for new documents. If you choose the command File | New, this template will always be set. It is completely empty and contains only the default "Normal" character style as well as the default "Normal" cell style.
Accordingly, the Normal.pmvx template is a suitable basis for creating a completely new template from scratch.
Important: You should not usually change the Normal.pmvx default template. If you want to do this anyway, you should be aware that these changes will affect all documents that are subsequently created based on this template.
For example, if you want to change the page format for all documents that will be created in the future based on the template Normal.pmvx, open this template, change the page format and save the template.
You can also choose a different default template for new files:
To do so, choose the ribbon command File | New 
(click directly on the icon itself), select the desired template in the dialog box and click on Set as default. From now on, PlanMaker will always offer this template as the default template when you create a new document.