Notes Client opens with an unexpected tab - running Designer

I often run designer with a custom perspective, the layout of which I find more useful on a portrait aspect monitor than the default perspective. Interestingly, the Notes Client has begun launching with an unexpected tab - one which contains this secondary Designer perspective.

Opening and closing Notes and the other clients in a variety of ways hasn’t yet resolved this odd behavior. I’ve restarted Notes 8 times this morning. Only once has Notes started “normally”. Launching it again, after the “normal” instance, I find the tab has returned.

Any thoughts as to the cause?

I can still launch the Designer Client. In fact, it appears to launch and function normally, even while running the instance within the Notes Client.

I anticipate that this will begin causing problems at some point, but thus far, everything appears to work in this configuration.

I appreciate any and all thoughts on returning my installation to “normal” with the least annoyance possible. Thanks.