No, sorry. As I explained earlier, the Resource Leveling command will never:

• Change assignment units
• Alter task duration

It is not a resource optimization tool. It will split tasks to allow other tasks to occur but otherwise its sole purpose is to delay tasks.

Thanks, I see.
Now as some method to still somehow support background tasks and Leveling I thought of some idea.
Is there a way to define some task, and give it a constraint that between Start and End day there will be at least some Minimal number of days?
This way the Leveling function will be required to split this task over a long period, even if total Work Time would allow it to complete very quickly.

You can define the task as spanning the duration of the project. Fix the duration (Task Information) and assign the work. Project will spread the work out evenly over the long duration dropping the assignment units to a low value.

Again- leveling will not change duration nor change assignment units.