Word meaning "kicking softly" or "brushing with the feet"?

Scuffing is a good choice here. It means to shuffle or scrape your feet along the ground (Dictionary.com reference). It would indicate reluctance or even some petulance depending on the context, like how a child might shuffle off after being to[ld to go to bed.

Scuffling is a similar word and possibly less harsh sounding (another Dictionary.com reference). I think shuffle is too light for what you want, and if scuff is too heavy, then this is about halfway between a scuff and a shuffle.

"Dusturbing" the sawdust on the floor.

I walked to the wall window, rustling the sawdust on the floor.

Typically used when walking through fallen leaves, I think it sets the right tone if there is a large amount of saw dust. Synonyms in this vein include: stirring, disturbing, raking, swirling, fluttering.

If you want to convey a light covering of sawdust, you could use a term that describes your feet more than the sawdust, such as:

I walked to the wall window, tracking through the sawdust on the floor.

Used in the meaning of

1 a : detectable evidence (as the wake of a ship, a line of footprints, or a wheel rut) that something has passed
    b : a path made by or as if by repeated footfalls : trail

_{Merriam-Webster, track}

Synonyms for this flavor: imprinting, furrowing, gouging, drifting (as in snow drifts), etching.

I walked to the wall window, toeing the sawdust on the floor.

Note that toeing is a sexual term according to UrbanDictionary, but I suspect that definition is something some prankster made up rather than an actual practice.

I walked to the wall window, padding across the sawdust on the floor.

I padded to the window through the sawdust on the floor.

dictionary.com

verb (used without object), padded, padding.
7. to travel on foot; walk.
8. to walk so that one's footsteps make a dull, muffled sound.

websters 1913

Pad, v. i. 1. To travel heavily or slowly. Bunyan.