Using File > Import and selecting image will only open the image as a new document. It is not possible to embed or link images into the current document.

System: Windows 11 23H2 (OS Build 22631.4317)
Inkscape: Inkscape 1.4 (86a8ad7, 2024-10-11)

Works here.

Inkscape 1.4 (aefccae, 2024-10-11) , 7z downloaded from GitLab Pipelines.
OS version:  Windows 11 Pro 22H2 (OS build 22621.4317)

Works fine! In a 4 pages document, did: File -> Import: Selected a PNG file ( 1.446 KB size).

Inkscape 1.4 (86a8ad7, 2024-10-11)
OS: Windows 11 Pro, 23H2, (Os Build 22631.4317)

Here is a GIF screen recording. I'm replicating the steps. Every time it goes directly to new document.

Looks like a bug.
I managed to reproduce this by setting SVG import mode to new in preferences.
I imported a PNG.

Yep! That's the fix. Thanks for troubleshooting for me!

I'm having the same issue.  Can't drag and drop PNG files into an existing SVG file.  Inkscape 1.4 will open a new file with only the PNG image.  I changed my SVG import mode from "New" to "Embed" and it will work once.  Then, when I try to import another PNG image, it resets itself to "New" and opens a new file.  I have to keep changing the import option from "New" to "Embed" in the preferences for every image I want to import.