Beaming problem

I should be able to figure out how to achieve this in the Notation Options/Beam Grouping, but - so far - no luck.

The only way I’ve been able to create the following beaming:
. . . has been by using the “beaming” feature while right-clicking my mouse.

How can I achieve this strictly via Notation Options/Beam Grouping?
So far, despite trying different options there, I keep getting this, instead:

Thanks, in advance, for any suggestions. . .

12/32 is interpreted as four groups of three 32nd notes, so Dorico is beaming according to the meter. Provided you never want to see those notes grouped separately as dotted 16th beats, you can create the time signature by typing [12]/32 into the popover.

As for an eighth crossing the half-bar, you’ll need to use Force Duration for that.

Thank-you very much, Daniel!

Do the numbers in square brackets [12]/32 indicate the number of “pulses” (in this case, 32nds) per “beat”, and the notation then beams according to the beats?

See Time signatures popover. With brackets you can specify beam groups. The default for 12/32 is written [3+3+3+3]/32 in the popover, but you can group them any way you like.

Thanks, Mark!

I was aware of that (and have used similar formulae for various hybrid signatures), but hadn’t put it together that - duh! - grouping all twelve 32nds together would result in their being considered as one ‘beat’, and thus result in all twelve being beamed together.