New block disappears from drawing

I cannot remember how to keep a newly created block on the screen. Please help.

Block Definition dialog box > Objects > select Retain.

Actually, RETAIN doesn't "keep a newly created block on the screen" - it keeps the entities that define the block on screen, and the block definition is just created.

If you want to create the block, delete the entities, and place a copy of the block in place, then choose "Convert to Block".

I stand corrected. Thank you.

I was also going to suggest the OOPS command, but that brings back the individual entities too...

That's probably a little used command these days...