If you rule out plugins I see 3 options left:
- drawing tracks right from the start with a 45°/90° round corner mode (see @jmk)
- after placing a track: select two neighboring tracks, RMB-click–>context menu–>Fillet tracks. This creates a arc-segment which connects both tracks
- working with the nightly development version v7.99. These version introduced the feature to assign every graphical copper item to a net: Post-v7 new features and development news - #24 by craftyjon
- waiting for the release of kicad v8 to get the last feature officially