You don't. The Dock is not a Finder window. It does not behave like one. What you're describing is the normal, default behavior.
Did the Deeper app change this and allow you to have folders in the Dock that behave similar to a folder in Finder?
Hey My friend, I want you to know I appreciate you teaching me about the dock not being a finder window. I love learning what finder is & all its functions but it's impossible to find educational topics out there at least I can't find any. idk if Quick Look is apart of preview or QuickTime ect.
To answer your question Gregg. Yes the Deeper App did change this & my god bro the app is amazing. you should def download the app it has so many features.
I created 3 screenshots for you & whoever may come across this post. I used a transparent folder for easy to see differences.
the images my not be in order. but I used the field names. invisible folder is the transparent folder.
Dock 1 image - what my dock looks like originally
Dock 2 image - Moving a folder to the dock creating a space (original behavior as you had mentioned)
Dock 3 image - No space can be created allowing for easy drag & drop files to the folders using the Deeper Application.
The answer is yes bro the deeper app allowed me to have folders in the dock that behave similar to a folder in finder.