How can I? All I found at the internet doesn’t match with my GUI. 
If File->save as template doesn’t do what you want, I don’t understand the question.
I don’t meant project template.
I want to save: “inserted FX and its config” to easily add it in another project. Like “DI Guitar distorted plugins” on a DI track.
And note that Ardour can also load up multiple plugins and their settings but NOT as a single step: you need to load the plugin and then choose the preset.
For those who want to know how to use the template after saving it:
When adding a track (right click in the blank space in the track list), choose your template from the Configuration dropdown.
Following up on this, I think one should read this: https://volse.anduin.net/~haraldei/ardour-track-templates/
In Ardour 5.12.0 I was able to store a bus template containing several plugins as a template. It became available from the template list after a restart of Ardour and then did the job perfectly. (Actually I saved one of my favorite reveb configurations consisting of some EQ and some impulse response stuff and other voodoo 
)