Thank you for your question,
Jinja2 is a templating engine for Python and should be possible to use it with Symphony BDK Python if the correct syntax is used. To ensure both Jinja2 & Symphony BDK Python is installed on your Python project, you will need the following packages are included in the 'requirements.txt':
From your screenshot - it looks like you are using FreeMarker syntax before the 'IF' condition. I would recommend referring to the Jinja2 documentation for the 'IF' condition:
If you wanted to use the FINOS Generator Symphony (https://github.com/finos/generator-symphony) to generate the Symphony BDK Python, you will find that there is a Python file called 'gif_activities' under the 'src' folder. This file will be referencing a Jinja2 template called 'gif.jinja2' under the 'resources' folder that is used to generate the user's name on a Symphony Elements form once a slash command is initiated.
We also have the following template example on the following FINOS GitHub URL that also uses Jinja2 with the Symphony BDK Python:
Please take a look and let us know should you require any further assitance or have any feedback.