Visualization: upgrading from 6 to 7

Hi everyone!

I have been googling quite a bit to try and find some info on how Kibana dashboards are affected during a Major migration from v6 to V7.

The only bit of info I found is here and that does not worry me too much.

Right now, I do not have access to the cluster I will be upgrading but I'm trying to find out how much effort will be involved depending on the type of visualizations or any other information I should collect beforehand.

If anyone has experience / more info on upgrading dashboards from v6 to v7 I would love to get your input.

Thanks.

Edit: As I will be upgrading to 6.8. first, maybe the upgrade assistant in Kibana will flag those viz for me?