Change the sizes of the emitters so the same time delivers less water.

5GPH for the main and 1GPH for the 20% (0r 10 and 2 ... depends on how much water you need)

It's the common way to deal with a mix of plants on a single line -

I already have 1/2 GPH emitters on the subsection. I'm not aware of emitters that run at 1/8 GPH or slower.

Emitters commonly come in 2, 1, and .5 gph sizes. There may be other flow rates available, check a cataloge (rainbird is probably your best bet) if you can't go smaller on your 'subsection', up the main part.

Dripworks sales 2 types of 1 quart per hour drippers that I use for small pots. one is pressure compensating the other is not.

Here is a link that might be useful: quart dripper

Cut into the drip line, put a small 1/2 ballvalve.

How long of a run of pipe do you have?

The main pipe for the subsection is about 15 feet. I like the idea of working in a ball valve. I'm also going to look for the Dripworks 1 qt/hr drippers.

Have you installed a filter/ reducer in this zone?