Hello again.
After some quick tests I confirmed that there are no limit on the OutSystems Maps side, but probably on the platform side.
I did a first test with 8000 places (as a best practice with an if condition around the markers list tight to the IsDataFetch attribute of you data sourece) and checked that for some reason I only got 857 consistently:

After I disabled the list virtualization I was able to get them all:

Hope this helps and internally I'll try to gather more information about this supposed limit.
Cheers,
GM