Yes, you're right, maybe I was not clear enough. Let's go with a better simpler try:

I would like to generate a odt template containing:

Structure: First page, spaces, between-paragraph distances, margins...
Static objects: Static text, images...
Sections gaps (I guess vars in LibreOffice) placed where section text should go.

This template will be the base of my documents. Well, once the template is ready, I need to generate final doc with the dynamics text. What I would like to do, and I don't know if it's possible, is to fill this sections (t1, t2, t3) in my template with markdown. Why I want to use markdown is to make possible to insert more than text in each section (bold text, lists, links, images...). An idea could be having 3 files, t1.md, t2.md and t3.md and use pandoc to fill the template like this:

render s1.md into s1 in the template
render s2.md into s2 in the template
render s3.md into s3 in the template

Ideally, I would like to insert a ToC at the begging. At this point, I should have my odt generated.

Trying to clarify: Section number and possition is fixed.

Let's forget about git or automations... I'm experienced enough to do that.

Thanks you all!