In Photoshop you can open up multiple photos in one window or tab, easily.
1. When You Have An Open Document
The process to add an image in an open document is easy. With the document open, click on File > Place Embedded. Then select the images you wish to add and click on Place. The image will come with ‘transform handles’, allowing you to move and resize it. Once you’re done with it press Enter and you have successfully added the image to your document.
2. When You Don’t Have a Document Open
When you don’t have a document open or wish to open up more than one image at once, do this: Head over to File > Scripts > Load Files Into Stack. then in the load layers box, click browse and select your images by holding CTRL or SHIFT. Once you have selected your images press Done
3. When You Want to Insert An Image From Another Document
Head over to Arrange and select 2-up Vertical or 2-up Horizontal. Your most recent image will be your active window and your photoshop tools will work on it only. Click the image and select move tool(Shortcut: V) then click and drag your image to another document. and that’s it.
Now you know 3 ways to open multiple images in one Window.