I just install 15.5.
I would like to configure kate in 15.5 as in 15.4.
I would like to configure kate without the necessity having a file open.
I would like to have toolbars in that order :
New,Open,Open Recent | Save,Save As, Save All | Close | Delete | Undo,Redo | Close current view, Split Vertical, Split Horizontal | Go Back, Go Forward | Highlighting | Comment, Uncomment
Sure! You can disable Welcome page to directly open new blank document when kate is opened.
Go to Settings → Configure Kate… → Session
Disable Option: Show welcome view for new windows
You can also setup the toolbar as you want. For that,
Go to Settings → Configure Toolbars…
Select Drop down option: Main Toolbar
Just Search and Double click on the options from the Available actions: . They will be added to your toolbar.
You can change position of each option up-down once actions are added to Current actions:.