13.25.17.5 Block Creation (available only when creating Designer Blocks)

Delete I/Os whenever possible - Deletes I/Os in the block during compile (except TRIBUFF and BIBUFF, because they cannot be removed). Useful if you have I/O's in your design but want to create a block anyway.

Add buffers on ports whose fanout is greater than <value> - Adds buffers on ports with a fanout greater than a value you specify. This option enables more predictable block timing. For example, if you have a net with a fanout of 100 the net will be unrouted. If you add a buffer, the output of the buffer is routed and the routing is preserved.