Is your feature request related to a problem? Please describe.
While testing mods I often chain machines together with creative storage units in between.
Items inputted to the creative storage unit stay in the IN slot, eventually locking the source machine or pipes.

Describe the solution you'd like
A creative storage unit/tank can safely void the inputted item/liquid when it is the same to which it's configured to.

Describe alternatives you've considered
Outputting to a block like Kibe's trashcan is an option, but makes it impossible to detect when other mods deposit the wrong items, or when machines produce the wrong items. Using a quantum storage unit would be fine for long-term testing, but is less optimal for stresstesting a sufficiently provisioned network.

@Katorone What about bucket or cell item in tank unit? Should they also void?

Only the actual liquid should be voided. Leftover cells or buckets should be returned like other tank units do.
I'm considering that handling the buckets/cells is part of the test setup. The player can either void excess buckets/cells, or they could be testing the network with a limited amount of cells, in which case it's useful to know if any go missing.