Currently, UE4 doesn’t support any Tablet Pen Pressure for all brush relative workflow, such as lanscape sculpting, vertex painting, foliage painting. Frankly, it is hard to find a modern CG software, which is including sculpting, painting workflow, without supporting tablet pressure. If UE4 supported tablet pen pressure, the level editing experience and efficiency would be greatly improved. Tablet pen pressure value may be designed to influence such as brush radius, sculpting strength, vertext color intensity, foliage density, randomness and so on. Besides, if the tablet pen pressure value could be tweaked by a curve editor, that would be appreciated.
UE4 does not support pressure at all as well as detection of different touch tool and touch state (hover/touch), like in Android APIs. So overall support it needed first, which might be useful also for games.
I entered a feature request for touch and pressure support, UE-16596 to be considered by the development staff.
+1 This is much needed. Overall, the painting/sculpting tools could use a little TLC
Btw, when the OP says “tablet” he means “Wacom type stylus tablet”, not an Android/iOS device type tablet