Hi there,
if you copy and paste to a new page, then GB won’t refresh the classIDs. So both pages will have blocks with duplicate classIDs.
However this in itself doesn’t cause an issue.
An issue arises if a page on the front end has duplicate blocks that were given different styles.
This can happen if I:
1. edited a Page and Copied a GB Block
2. created a Block Element eg. a Page Hero or a Footer and pasted my copied block into the element.
2.1 Made a style change to that block.
2.2 set the Block Element to display on the page i copied the block from.
What happens then, is both blocks get loaded with the same classID and whichever blocks CSS got loaded later would affect both.
In this example i would make a duplicate block.
So as long as a copied block isn’t being shown on the same page as its original eg. via an Element or a Widget area then there should be no issues.
If you find yourself reusing a lot of block content you created, then you may be interested in GenerateBlocks Pro which has a Local Pattern Library for you to save them to. And those can be added anywhere without any issues.