Nasdaq-100-APP-replaced-DLTR

In WL6 when performing an update for the dataset it was shown in the update log when there were changes to the dataset. Where do I see that information in WL8?

Re: update log. What you're talking about only concerned the Wealth-Data provider in WL6. In WL8 there's no equivalent.

Restart WealthLab (today) and you'll see new symbols in the corresonding Wealth-Data DataSet, like APP in the WD Nasdaq 100 DataSet.

When you use Wealth-Data DataSets for Portfolio Backtests, you get survivorship-free backtests (automatically).

See blog: Avoid Survivorship Bias with Dynamic DataSets

Are new symbols marked in any way so that they catch an eye when they are added?

No.
If using a dynamic DataSet is a problem, you can create your own using a current list of symbols and change it whenever you're ready for it. You can even make your own list dynamic and enter the dates when you made the change.