Hey together,
I am a big fan of the BPM addon. Currently I implemented the sending of emails via Service tasks, having the mail templates in the message template addon. This works so far, but for easier development it would be nice to have a seamless integration of the message template addon in BPM. So i would be able to select a message template being sent at the place of the Mail task. The main advantage would be the template designer which can be used and a decoupling of the template look and feel and the process itself. I have many customers, using the same processes, but all of them use different mail templates with custom text. 
Hello @manuel.hummler,
Thanks for the idea.
The BPM add-on has a “Send task” for sending messages. One implementation option is to add a drop-down list with message templates to the “Content” section.
Send Task - Email Sending Task :: Jmix Documentation
Is this solution right for you?
Regards,
Nikita
Hey Nikita,
yes, that’s a great idea! 
In addition, I’m facing the following challenge: I store the IDs of entities that are created during the process, and these entities should later be loaded so they can be accessed within the message template. Some of these entities rely on transient variables, which would also need to be enriched. So there are a few extra complexities involved.
That said, I believe this feature could bring significant value to the enterprise community, since many customers will likely want to manage message templates separately from their BPMN models.