Hi Royce
In Styler for APP land virtually everything in my experience is block based so you would normally apply your keep rules on the element objects in the stylesheet and add any extra conditions, contexts or source edit customisation rules there.
However if you cannot define logic for all cases and want a one off inline method for placing between elements keeping 2 unkept blocks together with conditions or rules via a PI you might be best off creating a custom function JS-FOM tag in an associated template (or in Styler in future releases) and apply this via a custom PI e.g. <?A3B2T [nopagebreak]>
It could depend on what you are trying to keep together its context and how thats been configured in APP/Styler.
Regards
Chris