E.g. a filter to only show plants which you have seeds of, or only plants that are capable of growing in that biome/season.
I think that the list of plants for outside plots already filters by biome. My current fort is half one biome and half another (I forget which ones at the moment), and I can only plant whip vine seeds (or, actually, any outdoor plants at all) in surface farm plots in what looks like one of the biomes. There could of course be another cause I'm missing.
I didn't know that it filters already, if it does, possibly since all farmable (have seeds) surface plants are just NOT_FREEZING and either DRY or WET, so it's rare to see the filter at work. Actually, it should only filter out whip vine/sliver barb/sun berry if you're not in a savage/evil/good biome, so it seems like you may have a mod that you've forgotten about? Since whip vine is [DRY][SAVAGE][BIOME:NOT_FREEZING], if you can plant whip vine, you should be able to plant all the other DRY plants too, since the lack of a SAVAGE tag is not the same as a NOT_SAVAGE tag AFAIK.
On another look, the new plant_crops.txt does improve things in that several plants are restricted to e.g. dry tropical savanna and/or grassland, and 1 each to dry tropical broadleaf forest and any tropical wetland (buckwheat and papyrus respectively). However, the majority still fall into either any_temperate, any_tropical, or not_freezing, and so as an extreme example, if you have a (fairly easy to find) embark with tropical savanna and tropical grassland, you'd have 23 possible crops by my count. Temperate climates get 14 crops, and non-tropical/temperate, NOT_FREEZING climates (taiga+tundra?) get 4: barley, alfalfa, rye and red spinach. Currently there are 8 farmable non-alignment surface crops. So most of the time there's going to be a significantly higher amount of crops.
I'm hopeful that at least garden plants will be in a separate list due to possibly being planted in garden plots instead of farm plots, but we'll see.
Interesting observations on garden plant biomes: caper bushes can grow in any desert or grassland; lentils and potatos in not_freezing; cranberries, bilberries and blueberries in any temperate, tundra and taiga.
Notes on tree biomes: the first 75% of the file are all tropical trees, with desert lime the only exception to any_tropical; the rest (from almonds) are any_temperate, with only bayberries as any_temperate+taiga. Another interesting fact is that they're only max trunk height 1, too, but might have heavy branches around them, so apparently they're a heavy, bushy sort of tree. For comparison, other max trunk heights range from 2-8, with 3, 2, 5 and 8 being fairly common (in that order).