Any idiom similar to "Hunger wall"?
Solution 1:
The expression I’m familiar with is busy work:
Busy work (also referred to as make-work and busywork) can refer to activity that is undertaken to pass time and stay busy but in and of itself has no actual value.
[Wikipedia]
Although I have heard it most used for work given in a school setting, it can be used for any worthless work.
For example:
The Scientific Reason Why Your Boss Gives You Busy Work
[The CheatSheet]