I’ve been working more heavily on the Mac side recently and have run into some quirks with Layout and Detail Layer settings as applied to viewports. On Windows, there was never the ability to apply Layout and Detail Layer settings to a modeling viewport, but I found on the Mac side that I was able to apply Layout and Detail layer settings, which was actually pretty helpful for controlling viewports without affecting the overall layer states.
Then I ran into an issue where I opened the file on Rhino for Windows and geometry was then missing from the model viewport even though the layer was turned on in the model layers. I had no way in Windows to make this geometry visible again in the modeling viewports, but it was all still there in the layouts. Instead, I had to open again on the Mac side, made sure the Layout and Detail Layer settings for the model viewport showed everything, save, and then everything was good in Windows.
Crisis averted for a bit, until Rhino for Mac 7.4 came out recently. It now appears that the Layout and Detail Layer settings can no longer be applied to modeling viewports. This makes it consistent with Windows, but now I have geometry saved in the file that I can not see in any of my modeling viewports and have no way of turning this geometry back on. HELP!