Just to update on the solution of this thread. Per mateuz suggestion (on this thread CustomJS Callback), after modifying the callback
cjs[i] = CustomJS(args=dict(column_layout=col[i], select=index, all_figures=figcol), code="""
// Replace with appropriate figure
var children = [...column_layout.children]
children[1] = allfigs.children[index]
column_layout.children = children
""")
It now works as intended.
Thank you guys.