Identify the pattern of notes used in a scale.
Either remember how many notes to skip or remember it as Tone Semi-tone or remember the swaras.
Use this information, start from any note on any string, play the pattern to get the scale for that particular note as the Root or Key.
Is it useful? This means that you don’t have to learn each scale, you have a better idea of what you are doing, you understand structures of music and the instrument much much better.

Indian guitar, carnatic, rhythm and chords, finding chords, playing by ear etc(Click to see)
Free resources at musicianself.com/rlo