A  
1  [a,2,[b,4]] 
2 
'a,2,[b,4]

3 
=A1.string@q(",")

4 
=A1.string(",")

5 
=A2.array@p(",")

6 
=A2.array(",")

7 
=A2.array@1(",")

Of A3~A7 the computation results are as follows:
Among the results, the member in blue is a sequence for you to double click and view.