I have it set to show only selected vertices in the Skin Weight Table and if I want to select all of the vertices in the table, I have to click it manually from the Edit menu up top. If I tried to use the default keybind, it would select all of the vertices in the main workspace instead of just in the weight table and when I switched the keybind, nothing happens when I try to use it. In fact, Select Invert and Select None don't work in the Skin Weight Table either, and just affect the model directly.