You should slide further to the left - even after you moved the breakpoint to 900 px there will always be a change of view at the old breakpoint of 800 px - even without a breakpoint there...
I want the view of 799 pixels upto 899 px = only the hamburger - no menu submenu or toggle menu - only the hamburger...

You need edit the header code in the parent container and replace every instance of max width 800px to 899px

https://youtu.be/XtwXTMO2gs4

(Wait 5 mins for it to finish uploading)

Puh - thank you - that's it
Do ypou know how one can find out before using a component, if it can be changed without coder knowledge ?

But a christal ball,