How to select feature (row) in QGIS 3 attribute table using keyboard cursor? I can't find a hotkey for this. Is this even possible?
The problem with this kind of requests is that you need some value from the attributes table for selecting one or more features or click or drag in left column of attributes table, with left button of mouse, in combination with Shift or Ctrl keys of keyboard. So, it looks as not possible "to jump" over left column of attributes table with cursor keys for this task. On the other hand, if you select one or more features, cursor keys cannot be used for deselecting. Shortcut keys for this task are Crtl+Alt+A (all layers) or Crtl+Shift+A (active layer).
In following image it can be observed that, by default, only 'Select Features by Expression' (Ctrl+F3) and 'Select Features by Value' (F3) are available. I tried my own combination by using cursor keys and its behavior was not as expected.
I also tried out F3 keyboard Shortcut with world_borders layer. Behavior can be observed in following image. Afterward, I put arbitrarily 127 in CAT and clicked 'Select Features', 'Zoom to Features' and 'Close'; respectively.
Result was as follows. Attributes Table with selected features was displayed with Shift+F6 keyboard shortcut.
As conclusion, I think the best solution is dragging in left column of attributes table, with left button of mouse in combination with Ctrl key of keyboard, for selecting multiple features, inclusively, not consecutive in Attributes Table. For deselecting, Crtl+Alt+A (all layers) or Crtl+Shift+A (active layer).