Highlighting folder in which a new folder is to be created. Then clicking New Folder button in top toolbar does not create folder in sellected folder, but creates folder in main directory tree.
Right click folder , the context menu has no choice to create a new folder.
Using Windows 10 Pro x64 with all latest updates.
Using Dopus lastest beta version. This issue has been since start for Dopus 13.
Not really an issue : that button never created a subfolder of the selected folder but a subfolder of the lister current folder.
Nevertheless, I had the same expectation due to the newly introduced foldable/unfoldable folders in Opus13.
What you can do :
Solution 1
Modify context menu for folders (Settings/File Types, then find "All the folders") and add a command (Opus function) either :
CreateFolder : will trigger the popup window to let you specify folder name, or
CreateFolder INLINE "{filepath$}/New Folder" : will create a folder named New Folder and instantly enter inline rename mode.
Solution 2
Enter either of these commands (according to your liking) in a button (with a hotkey if you want) that you will place wherever you want. Mine sits near to the breadcrumbs.
You will find several ideas in this thread:
Double click "All Folders".
It opens :
Go to the context menu tab, click "+ New"
Type : Opus Function
Give a name (and an icon if you want) to the action
Function : Standard function
In the editor, type in the function you prefer (here is just CreateFolder)
Then you can decide where it will appear in the menu.
If you want ideas for code for creating folders in all possible situations, look at the code in this three button button:
Create New Folders.dcf (6.4 KB)
I have this thread bookmarked as my thoughts agreed with @PassThePeas .
I made a new button under my default New Folder Button named 'New Expanded Folder' that does this instantly in inline rename mode.
I don't mean to disagree with you @jinsight , it is only that I have these things worked out differently than you. 
I don't want ideas by code, I don't want to be adding anything.
I do not see what the big issue is. Prior to version 13 one right clicked on the folder one wanted to create a sub folder, which brought up the context menu, which then gave the option to create a new folder. This no longer works in version 13.
This is supposed to be the place to get tech support from the creators of Dopus, so where is the update to Dopus 13 to fix what Dopus has always done in the past?
It did not work that way in Opus 12. You couldn't expand sub-folders in Opus 12, except via Flat View, and the context menu didn't have a Create Folder option inside it by default.
We have provided you the way to get what you want. It's very easy to set up.
The problem is almost even easier if all want is a context menu to create a new folder from a selected folder within expanded folders.
Settings -> Filetypes -> All folders
Under the context menu tab:
Press New.
Select Type: Run an Opus function
Label the text box with the name you want to display in the context menu.
The command code can be either createfolder if you want a GUI to name the folder,
or CreateFolder INLINE if you want an immediate inline rename.
But still, I agree with what @PassThePeas posted.
I could swear on a stack of Bibles this was doable in Dopus 12.
Thank you for above work around.
It was doable in 12 the same way it's doable in 13, by adding a command to the context menu. Maybe you were using a pre-made configuration that included the command by default or something.