Figure 3. This simulation shows how a galaxy halo, like our own, may have been
built up by the accretion of 50 dwarf galaxies colliding with the galaxy at various
times during the last 10 billion years. The unit of distance is the kpc, or kiloparsec, where 1 kpc is a little more than 3000 lightyears. GAIA would be able
to detect the fossil streams of these ancient merging events (Courtesy of Paul Harding)
Twenty years later, have results from GAIA been used to generate any data of this nature, identifying groups of stars that are likely to have come from nearby dwarf galaxies merging with our own?
Malhan et al. (2018) summarise progress so far (the Gaia astrometry is improving all the time as more data are collected) using Gaia DR2 data. In particular they produce "panoramic maps" of streams in the Galaxy halo, which I believe is exactly what you are looking for (see below).
Coherent tangential velocity structures, a.k.a. "streams", seen in the southern Galactic hemisphere by Gaia DR2 - from Malhan et al. (2018).