This is normal behavior. Other Toad versions behave the same way.
As a possible workaround, open a new Editor Tab via the Editor menu | New Tab | click "PL\SQL Style". This avoids the 1 sec delay when using the "+" (plus) sign to open a new tab in the Editor.
Another possible workaround is open two Editor Windows. One for ‘PKS/PKB’ tabs and the other for ‘New SQL’ tabs. Switching between the two Editor Windows will be always quick. However, ensure the Editor Windows are not ‘maximized’ (do NOT maximize the internal windows in Toad) or the 1 second delay will come back.
We value our customer’s needs and every Toad version is created and designed with many user inputs in mind. Please submit an Enhancement Request for Toad to make the abovementioned issue faster. Please visit the Toad Idea Pond site to log an enhancement request. This site is solely dedicated to tracking customer enhancement requests and allowing the user community to vote on the most useful feature. The Toad Development Team personally monitors this website and provides customer feedback on their enhancement requests.