For these parameters, you need to modify the code contained in minetest_game/mods/default/nodes.lua
There used to be a global variable for water and lava viscosity, but now you have to edit the code of their registration :
https://github.com/minetest/minetest_ga ... s.lua#L911Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.
You have to do it for both source and flowing, on every node you want to change.
The radius of flow is a builtin parameter and I don't think it should be increased nor dicreased (knowing that water's parameter for the flowing drawtype is limited).