remove \n after replace ” ” in kdb+

Here is an example of how to use ssr to achieve the desired trimming you require in a table setting:

q)t:([]a:1 2 3;b:("\nThis is sample code";"More good sample code";"\n More sample code"))
q)t
a b
-------------------------
1 "\nThis is sample code"
2 "More good sample code"
3 "\n More sample code"
q)@[t;`b;{trim ssr[x;"\n";""]}@']
a b
-------------------------
1 "This is sample code"
2 "More good sample code"
3 "More sample code"

Hope this helps.