I too at first had some difficulty as to when to use the headlight on blink- or stay-on mode whenever I'm riding. I know I had to consider the main factors: road or MUP, fellow cyclists and pedestrians/runners/joggers/etc.

Based on what I've read from other posts and my riding experience this year, I use:

blinker mode - when it's daytime (like summer-like daytime) no matter whether I'm on the trail or on the road. I aim my light a little more horizontal; and

full-on mode - as soon as the natural light becomes a bit too dim for comfort whether on the road or on the trail. I aim my light more toward the road in order not to annoy motorists, cyclists and pedestrians.

Another way to put it: blinkers to be seen, full-on to see.