I’m not sure I can explain this quickly, but I’ll have a go:
Dorico makes one automated decision per phrase, where a phrase is defined as the stuff between rests. Depending on the writing, this can mean that a phrase - and a single condensing decision - can last for a single note or multiple pages.
You can tell Dorico to start a new phrase anywhere you like, by inserting a Condensing Change from the Engrave menu: you need to flick the switch(es) for the relevant player(s), but you don’t necessarily need to change any of the other parameters in the dialog.
Dorico’s general approach to condensing can be influenced, at the flow level, from Notation Options > Condensing. Each of the settings in that dialog can be locally overridden from the Condensing Change dialog, as often as you like.
edit: I suppose for clarity I should add that the pictures in Notation Options > Condensing are crucial, as are the little textual explanations underneath some of the options. Many of these options are dependent on each other, so bear in mind that if you can’t work out why some option down at the bottom of the dialog isn’t working, it may be because something in a completely different bit of the dialog is set in a way that’s incompatible with the music you’re throwing at Dorico.