Is it possible for the driver to display a "warning" message / pop up window? The specific need is for radio settings that if set together cause some undocumented (but maybe desired for some users) behavior, and I woull ike to make sure they are aware, (see https://chirp.danplanet.com/issues/9939 for specific details).

Not in general, no. The drivers need to work in isolation from the UI. There are some canned warnings you can expose, which the UI will show to the user like before they download, upload, etc, but not where you're looking for.

Best thing to do is raise an exception when they try to set something that conflicts with another setting. That probably shows the exception message to the user. If not, we should make it do that.

--Dan