Just a small/final update from my side. With your input I managed to get my template to ask for title and two tags (category and subject) and place the information correct. Great fun fiddling with it to understand how things work.
I leave the code here, in case other want to so something similar.
<%*
let title = tp.file.title
let sSubject = ""
let sCategory = ""
if (title.startsWith("Untitled")) {
title = await tp.system.prompt("Title");
} await tp.file.rename(title);
sCategory = await tp.system.prompt("Category");
sSubject = await tp.system.prompt("Subject");
setTimeout(() => {
app.fileManager.processFrontMatter(tp.config.target_file, frontmatter => {
frontmatter["category"] = sCategory;
frontmatter["subject"] = sSubject;
})
}, 200)
-%>