Inherit another template or optional variables?

[jeremywillans]

Is your feature request related to a problem? Please describe.
I have several fairly duplicated templates which have something minor as a difference, for example an extra service-data parameter or one with an extra option.

Describe the solution you'd like
Is there a way to either inherit config from another template, or exclude parts of the template based on if you have specified the particular variable?

Describe alternatives you've considered
Multiple templates

[ildar170975]

Similar functionality may be achieved by "cascading" templates & using yaml anchors:

template_1:
  default: &ref_default
    - var_1: ...
    - var_2: ...
    - ...
  card:
    ...
...
template_2:
  default: *ref_default
  card:
    ...
    - &ref_calling_template_1
      type:custom:decluttering-card
      template: template_1
      variables:
        - var_1: '[[var_1]]'
        - var_2: '[[var_2]]'
    ...
...
template_3:
  default:
    ... new default values
  card:
    ... another functionality
    - *ref_calling_template_1
    ... another functionality

[jack3308]

Just to confirm, this approach would only work when using the yaml development method and not the UI, correct?

[ildar170975]

yaml-anchors are supported in yaml mode only.