Hi. I'm still leaning the software, but making good progress ( I think). What I'd like to learn is how to create a new pattern fill. I'd like to create a lace effect and add it to a layer. There aren't any appropriate pattern fills in the default settings, so I'm wondering if new fills can be created. Or, can this be done by creating a new brush?
Any ideas?

Patterns are .png files or GIMP pattern (.pat) files. They're stored in the krita resources folder, in the patterns folder.
This is C:Users\{username}\AppData\Roaming\krita\patterns
If you manually put them in that folder you'll need to restart krita before they're available in the Patterns docker.

You can also import them using Settings -> Manage Resources -> Import Patterns which makes them immediately available.

You can make your own, no problem, and the .png file can have transparency if you like.

"You can also make you own, no problem"
Thanks, but How? That's where I'm stuck a the moment. Is there a tutorial somewhere that shows the steps?

Since a pattern file can be a .png file, which is a very common image file format which can have transparency in it, you can make it in krita or any digital imaging application. Patterns are usually small in size, maybe 100 - 200 pixels square but you can make them more or less any size you like as a created image and then Export the image as a .png file.

Making a pattern file is easy. Making a nice looking regular line pattern is a little more difficult. Making an 'organic' looking pattern that tiles well with no obvious edge joins is much more difficult and needs skill and experience.

If you go to Google Images and search for "seamless texture" (or "seamless lace texture") you'll find lots of them, often attractive and very good quality. Many are covered in watermarks and need registration sign-up or payment to download but you can find free ones.

A Google or Youtube search for "make seamless texture" or "make seamless pattern" will give lots of results for tutorial videos or articles, mostly for Photoshop but the techniques can be used in krita.

Within krita there's the View -> Wrap Around Mode which shows what your image would look like if tiled and lets you design/edit a pattern 'live' on-canvas.