Strange Artifact in Preview Mode

With the current release version of Blocs and the latest BETA version when I go into PREVIEW mode I now get this artifact on the righthand side of the screen and centered vertically. It looks somewhat like a scrollbar thumb but it is further in from the edge of the screen.

I have no idea where this came from or what might causing it, it is present on all of the pages of my site.

Any one have any ideas?

It’s actually a very handy feature. Try to drag it to see how your website design adjusts to different size of the window.

Aloha Eldar:

Wow that is a great feature, is that something new as I just noticed it now, of course I did not try dragging it but now that I try it that is a fantastic feature. Thank you so much for solving this for me and pointing out this great feature!

Why have I not seen this before or is this a new feature?

It’s been there since the introduction of Blocs 3 I believe.

Never showed up for me until the most recent release, maybe there was some setting where I had it turned off. Either that or I just never noticed it, which is entirely possible!