Songs, chains and scratchpads

Today I’ve started to explore songs and chains.
I now know how to edit songs
I understand how to create chains in detailed or quick mode on the scratchpad

But what I don’t understand is why my scratchpad is empty once I press stop?
Sometimes the scratchpad ends up as a song line, sometimes not
For some reason I can’t find in the manual why this is happening.
Also sometimes I only see 1 pattern icon in the bottom left corner, sometimes I have a view of nearly the whole bottom row.

Can someone please explain to me what I’m missing getting scratchpads committed in a song and not being erased? And the differences in the 2 views?