cannot unassign an algorithm to a block in the experiment.
After choosing an algorithm for a block in an experiment it is not possible to assign no algorithm to that block. It is only possible to choose from certain algorithms. This is not the case for the Database though. If there is a problem in the toolchain and you want to find out where the problem is it would be a good option to unassign an algorithm without deleting the whole block.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information