Yes. For light painting, multiple shorter exposures can be combined to simulate a longer exposure, as long as the camera and scene stay perfectly aligned. In principle, adding the light from two exposures is equivalent to one longer exposure.

The main limitation is gaps: if there is any time between exposures, the light trail will have breaks. That means this works best if you split the writing into separate parts or words and combine them later in an editor using layers or lightening/additive blending. A very dark scene helps, because it reduces visible background changes and ghosting.

If the room or subject is lit, differences between frames can make compositing harder. Keeping everything else dark makes the light writing much easier to merge cleanly.

For phones, combining video frames could work only if each frame is exposed continuously with little or no gap between them. If there are gaps between frames, the light trail will be discontinuous. Multiple stills can also be combined the same way if the phone and scene remain fixed.