[ENHANCEMENT] Support referencing variables in 'Min step' field

[AntoineThebaud]

Description

Closes #1724.

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• Pull request title follows the [<catalog_entry>] <commit message> naming convention using one of the
  following catalog_entry values: FEATURE, ENHANCEMENT, BUGFIX, BREAKINGCHANGE, DOC,IGNORE.
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[Gladorme]

I think it will need a validation check to be sure the variable is a DurationString. And maybe it will remove some casts

[AntoineThebaud]

I think it will need a validation check to be sure the variable is a DurationString. And maybe it will remove some casts

Added this as a comment, to be addressed later.