Everytime I click the flexbox buttons (under options, top right hand side of a screen), it seems to set the setting for the current responsive screen breakpoint. It's very annoying having to => expand the 'flex container', click on the drop down, un select the drop down.
Is there an option to have it select all break points by default?
If I understand your complaint correctly, you don't like the fact that the flexbox "shortcut" buttons only apply the flexbox setting to the particular screen size (breakpoint) you are working on your current workspace.
This is probably because you are not designing your website "mobile first", which is how the Bootstrap 4 framework is meant to be used. If you design at the XS size, when you click the shortcut buttons at the top of the Flexbox options, it will apply your setting at the base size (which is XS) and all the sizes above will inherit that setting.
But if you are designing at a desktop size, like LG or XL, and you click one of the shortcut flexbox buttons, it will only apply the setting to the particular size you are working on. This is by design, and the way it's supposed to work.
If you don't want to work from a mobile-first workflow, then you're probably better off not using the shortcut buttons, and just applying your flexbox settings directly from the expanded submenus.