Great start. I've just taken the plunge with PixInsight so seeing your workflow is really interesting. You can increase the saturation via the CurvesTransformation tool. Click on the S on the bottom-left under the curve and move the curve to adjust the saturation.
There are also useful scripts for combining narrow-band data that are worth playing with.
I have found
Harry's astro shed a good place to start for LRGB images, but there is lots to learn. I'm still working out the best workflow for my images.
Cheers,
Aaron