Thanks for your suggestions, I’ll continue to play with the settings in order to get a more responsive dashboard. In the local network (with your suggested settings for the simple value panel) it takes between 2-3sec before the value is updated in UI after clicking on the lov panel. If I am connected from outside (via 4G mobile network and VPN) it takes at least 10 sec but often even more. Other websites (also one hosted on the same Synology) are still pretty responsive in VPN but I can see there is a lot of data traffic created when displaying my dashboard (10kB to 100kB per sec).
I have a Synology DS 115.