This should be make explicitly clear.

Comments

Title:README.txt does not say about clear cache when adding new custom markersREADME.txt does not say to clear cache after adding new custom markers
Version:6.x-1.0-beta6» 7.x-1.x-dev

This is still relevant.

Title:README.txt does not say to clear cache after adding new custom markersAdding new custom markers should clear necessary caches instead of requiring "Clear all caches" button click
Component:Documentation» Code

Well really GMap module should clear the relevant cache when adding a new custom marker. This isn't a documentation problem so much as a shortcoming of the module properly clearing the caches when it needs to.