K.E.R.N.E.L keeps a ledger of every science experiment in your career.
The R&D page: the whole solar system on one map. Kerbin is selected, so the sidebar lists its biomes and the science gathered in each, with "?????" for biomes not yet visited.
Modded planets: a second star gets its own system in the picker along the top, tinted by its light. Its planet, moon and moon of a moon are drawn from their own textures, with their science in the sidebar.
The ledger window in flight: every body, region and experiment in one tree, with the science gathered out of what's available at each level.
The ledger window in the VAB, opened from its own button on the toolbar, to check what science is left before you build.
mods folder (Kerbal Space Program 2\mods\). It contains a KERNEL folder, so you end up with mods\KERNEL\.Raw stats are from the beginning of time until now. Each follower and download entry represents one hour of data. Uneventful hours are omitted.