Hot Key remap selection has restrictions?

Hello everyone.
I’m trying to remap key in SCR to mimic the hot key setup I have in SC-2. However, I’m unable to set space bar as a hot key. Is there a reason for this or a way around this restriction?

Here is an example. I select a probe. I want to map Build Structure to space and Build Advance Structure to E. I would then map those two keys in the same manner for starting unit of the zerg and terran. Thus no matter which race I play I will have space and E mapped in the same manner. The starting building for each race is mapped to E. This allows me to select a builder > Space > E to start a Nexus, Command Center, or Hatchery. This is an improvement over the default key map.

SC1 and SC2 are completely different in the underlying architecture。So the hotkeys can only be mostly the same, not exactly the same,So I suggest you set it manually。