I'm posting this in the support forum instead of as a bug, as I'm sure I'm just missing something obvious and I'm just not that comfortable with the new interface yet.

I use demo.limesurvey.org to test this, so that we know it's not an installation issue on my side.

What happens is when I go to add an entry in Panel Integration, it doesn't seem to save it after I click to save the survey settings. Screenshots attached.

So the process I follow is this:
1. Add new survey
2. Survey Properties | General Settings & texts | Panel Integration
3. Click Add URL Parameter, then type in "abcdefg" for Parameter Name, No Target Question, and click Save. It shows up fine in Panel Integration.
4. Click Green Save button at top to save Survey Settings. See "Survey settings were successfully saved." message.
5. Click on Panel Integration again, and the parameter from #3 is now gone.

I also attached the .lss file as well in case that helps. What am I missing?

Looks like this was a bug, and it has been fixed:

Changes from 2.06+ (build 160206) to 2.50+ (build 160210) Feb 10, 2016
-Fixed issue #10321: Submit panel integration form when updating survey settings (Olle Haerstedt)