Is it possible to retrieve the coordinates (in the plot) for a HighlightTrack object? Consider this code:

library(Gviz)
library(TxDb.Hsapiens.UCSC.hg19.knownGene)

transcriptName <- "uc001aaa.3"

# Get exons in transcript:
gr <- GenomicFeatures::exons(
  TxDb.Hsapiens.UCSC.hg19.knownGene,
  vals = list(tx_name = transcriptName),
  columns = list("EXONNAME", "TXNAME", "GENEID"))
gr <- expand(gr)
# Remove extra transcripts I didn't want:
gr <- gr[mcols(gr)$TXNAME == transcriptName]
# Add $transcript mcols for grouping
mcols(gr)$transcript <- mcols(gr)$TXNAME
# Create tracks:
tr <- Gviz::GeneRegionTrack(gr)
htr <- Gviz::HighlightTrack(
  trackList = tr,
  start = 11874,
  end = 12721)
# Plot
res <- Gviz::plotTracks(htr)

# Now what's in res?
res
# $GeneRegionTrack
# GeneRegionTrack 'GeneRegionTrack'
# | genome: hg19
# | active chromosome: chr1
# | annotation features: 3
#
# $titles
# An object of class "ImageMap"
# Slot "coords":
#   x1 y1   x2  y2
# GeneRegionTrack  6  6 39.6 685
#
# Slot "tags":
#   $title
# GeneRegionTrack
# "GeneRegionTrack"

# I'm able to get the coordinates of the transcript:
trCoordinates <- Gviz::coords(res$GeneRegionTrack)
trCoordinates
#               x1     y1       x2      y2
# exon_1  52.26409 90.875 172.0768 600.125
# exon_2 303.09009 90.875 339.7467 600.125
# exon_3 509.45302 90.875 912.6753 600.125

# But I don't see any options for retrieving coordinates for the HighlightTrack

Those are currently not being returned in the plotTracks results. Will have to take a look at this in order to include.