Hi all,
I have the same problem of this post:
https://powerusers.microsoft.com/t5/Building-Flows/Access-Variable-at-Runtime/m-p/351891
I want:
1) to save on Sharepoint my templates.
2) read their content
3) substitute variable (I cannot find a solution to this issue)
The proposed solution is not so clear.
This is my flow:

My file content is:
This is the variable in File: @{variables('VariableInFile')}
As you can see in the last compose the variable was not replaced.