Example code generated with ScriptUI Dialog Builder: https://github.com/joonaspaakko/ScriptUI-Dialog-Builder-Joonas

Dialog Example - Import Multiple PDF pages.jsx

/* 
Code for Import https://scriptui.joonas.me — (Triple click to select): 
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*/ 

// DIALOG
// ======
var dialog = new Window("dialog"); 
    dialog.text = "Import Multiple PDF pages"; 
    dialog.orientation = "row"; 
    dialog.alignChildren = ["left","top"]; 
    dialog.spacing = 10; 
    dialog.margins = 16; 

// GROUP1
// ======
var group1 = dialog.add("group"); 
    group1.orientation = "column"; 
    group1.alignChildren = ["fill","top"]; 
    group1.spacing = 10; 
    group1.margins = 0; 

// PANEL1
// ======
var panel1 = group1.add("panel"); 
    panel1.text = "Page Selection"; 
    panel1.preferredSize.height = 205; 
    panel1.orientation = "column"; 
    panel1.alignChildren = ["left","top"]; 
    panel1.spacing = 10; 
    panel1.margins = 10; 

var statictext1 = panel1.add("statictext"); 
    statictext1.text = "Import PDF Pages:"; 

// GROUP2
// ======
var group2 = panel1.add("group"); 
    group2.orientation = "row"; 
    group2.alignChildren = ["left","center"]; 
    group2.spacing = 10; 
    group2.margins = 0; 

var edittext1 = group2.add("edittext"); 
    edittext1.text = "1"; 
    edittext1.minimumSize.width = 60; 

var statictext2 = group2.add("statictext"); 
    statictext2.text = "thru"; 

var edittext2 = group2.add("edittext"); 
    edittext2.text = "1"; 
    edittext2.minimumSize.width = 60; 

// PANEL1
// ======
var checkbox1 = panel1.add("checkbox"); 
    checkbox1.text = "Reverse Page Order"; 

var statictext3 = panel1.add("statictext"); 
    statictext3.text = "Start Placing on Doc Page:"; 

var edittext3 = panel1.add("edittext"); 
    edittext3.text = "1"; 
    edittext3.minimumSize.width = 60; 

var checkbox2 = panel1.add("checkbox"); 
    checkbox2.text = "Map to Doc Pages"; 

// PANEL2
// ======
var panel2 = group1.add("panel"); 
    panel2.text = "Sizing Options"; 
    panel2.preferredSize.height = 160; 
    panel2.orientation = "column"; 
    panel2.alignChildren = ["left","top"]; 
    panel2.spacing = 10; 
    panel2.margins = 10; 

var checkbox3 = panel2.add("checkbox"); 
    checkbox3.text = "Fit to Page"; 

var checkbox4 = panel2.add("checkbox"); 
    checkbox4.text = "Keep Proportions"; 

var checkbox5 = panel2.add("checkbox"); 
    checkbox5.text = "Bleed the Fit Page"; 
    checkbox5.value = true; 

var statictext4 = panel2.add("statictext"); 
    statictext4.text = "Scale of Imported Page"; 

// GROUP3
// ======
var group3 = panel2.add("group"); 
    group3.orientation = "row"; 
    group3.alignChildren = ["left","center"]; 
    group3.spacing = 10; 
    group3.margins = 0; 

var statictext5 = group3.add("statictext"); 
    statictext5.text = "X%:"; 

var edittext4 = group3.add("edittext"); 
    edittext4.text = "100"; 
    edittext4.minimumSize.width = 40; 

var statictext6 = group3.add("statictext"); 
    statictext6.text = "Y%"; 

var edittext5 = group3.add("edittext"); 
    edittext5.text = "100"; 
    edittext5.minimumSize.width = 40; 

// GROUP4
// ======
var group4 = dialog.add("group"); 
    group4.orientation = "column"; 
    group4.alignChildren = ["fill","top"]; 
    group4.spacing = 10; 
    group4.margins = 0; 

// PANEL3
// ======
var panel3 = group4.add("panel"); 
    panel3.text = "Positioning Options"; 
    panel3.preferredSize.height = 205; 
    panel3.orientation = "column"; 
    panel3.alignChildren = ["fill","top"]; 
    panel3.spacing = 10; 
    panel3.margins = 10; 

var statictext7 = panel3.add("statictext"); 
    statictext7.text = "Position on Page Aligned From:"; 

var dropdown1_array = ["Top Left","Top Center","Top Right","Center Left","Center","Center Right","Bottom Left","Bottom Center","Bottom Right","-","Top - Relative to spine","Center  - Relative to spine","Right  - Relative to spine"]; 
var dropdown1 = panel3.add("dropdownlist", undefined, dropdown1_array); 
    dropdown1.selection = 0; 

var dropdown2_array = ["0","90","180","270"]; 
var dropdown2 = panel3.add("dropdownlist", undefined, dropdown2_array); 
    dropdown2.selection = 0; 
    dropdown2.text = "Rotation:"; 

var statictext8 = panel3.add("statictext"); 
    statictext8.text = "Offset by:"; 

// GROUP5
// ======
var group5 = panel3.add("group"); 
    group5.orientation = "row"; 
    group5.alignChildren = ["left","center"]; 
    group5.spacing = 10; 
    group5.margins = 0; 

var statictext9 = group5.add("statictext"); 
    statictext9.text = "X:"; 

var edittext6 = group5.add("edittext"); 
    edittext6.text = "0"; 
    edittext6.minimumSize.width = 40; 

var statictext10 = group5.add("statictext"); 
    statictext10.text = "X:"; 

var edittext7 = group5.add("edittext"); 
    edittext7.text = "0"; 
    edittext7.minimumSize.width = 40; 

// PANEL4
// ======
var panel4 = group4.add("panel"); 
    panel4.text = "Placement Options"; 
    panel4.preferredSize.height = 160; 
    panel4.orientation = "column"; 
    panel4.alignChildren = ["fill","top"]; 
    panel4.spacing = 10; 
    panel4.margins = 10; 

var dropdown3_array = ["Art","Crop","Trim","Bleed","Media"]; 
var dropdown3 = panel4.add("dropdownlist", undefined, dropdown3_array); 
    dropdown3.selection = 0; 
    dropdown3.text = "Crop to:"; 

var checkbox6 = panel4.add("checkbox"); 
    checkbox6.text = "Place Pages on a New Layer"; 

var checkbox7 = panel4.add("checkbox"); 
    checkbox7.text = "Ignore Font and Image Errors"; 

var checkbox8 = panel4.add("checkbox"); 
    checkbox8.text = "Transparent PDF Background"; 
    checkbox8.value = true; 

// GROUP6
// ======
var group6 = dialog.add("group"); 
    group6.orientation = "column"; 
    group6.alignChildren = ["fill","top"]; 
    group6.spacing = 10; 
    group6.margins = 0; 

var button1 = group6.add("button"); 
    button1.text = "OK"; 
    button1.justify = "center"; 

var button2 = group6.add("button"); 
    button2.text = "Cancel"; 
    button2.justify = "center"; 

dialog.show();