Did you try saving the template as .indt?https://indesignsecrets.com/topic/where-do-i-save-indt-template-files
Or do you want to synchronize all the styles based on one master document of the book?Create book files with Adobe InDesign (Synchronize book documents section)
Yes the template is a .indt file. And I want to synchronize all chapters with the indt. If possible.
btw: indesign cc 2017
Since you have your documents (chapters) as part of the book the recommended workflow would be to synchronize all the styles based on one master document of the book Compose CJK characters in InDesign (Synchronize book documents section)
When you synchronize documents in a book, the items you specify—styles, variables, master pages, trap presets, cross-reference formats, conditional text settings, numbered lists, and swatches—are copied from the style source to the specified documents in the book, replacing any items that have identical names.
If items in the style source are not found in the documents being synchronized, they are added. Items that are not included in the style source are left as is in the documents being synchronized.
I know. But that 'style source'/'master document' cannot be a .indt file? That is my question
No, the master document can be an "indd" file.
I do not know if this helps or if this is the best method, but I would use it had i been in your place..
1. Open the template file and save it as a "temp.indd" document
2. Add this "temp.indd" document to the book
3. Synchronize all the book documents using "temp.indd" as the master document (please check what all you want to synchronize first using synchronize options dialog box)
4. Once synchronized all the styles etc in the non master document would be redefined to the style defination of the master document "temp.indd"
5. Remove "temp.indd" from the book
FWIW: An InDesign template *.indt document is nothing but a *.indd file.
Just with a different suffix. So renaming the template should also work. Or duplicating and renaming.
Structurally the files are identical. The file extension triggers InDesign to open a copy instead of the original by default for .indt files, and the opposite for .indd.
Changing the extension will convert one to the other.
Thanks for reminding