Edit:
When posting, I thought, this problem is only present, when expression is used in the first column. This was wrong. I updated my post
Hey!
I can use this expression in my dmn-table:
not("XY", "ZZ")
and this
"XY", [CTRL+RETURN] "ZZ")
This linebreak help use to keep longer texts and lists better readable and it prevents the editor from showing double-monitor-width-columns 
When using this within a not-expression, the engine reacts with a
FeelSyntaxException:org.camunda.bpm.dmn.feel.impl.juel.FeelSyntaxException: FEEL-01001 Syntax error in
expression ‘not(“XY”, [real linebreak in colsole]
“ZZ”)’: Expression should have format ‘not(…)’