O2EM "Clear" key

[CKlemow]

Sorry if this is a dumb question, but I've searched the support files that came with O2EM and searched Google and can't seem to find the answer:

 

What button, if any, is the Odyssey 2 "clear" key in O2EM? I've read online that it's Backspace, but this does not seem to work. (I'm trying to program a custom maze in K.C. Munchin.)

 

Thanks!