You should be able to do it by positioning two Rectangles, one below and one above in the xml. Note that if you want a more customisable progress bar you should create one using a design tool like figma or marvel and adding it to the project as a Poster. Then, in your .brs file you add a observer to the video position and set video.enableUi = false. Something like this:
m.emptyProgressBar = m.top.findNode("emptyProgressBar")
m.colorizedProgressBar = m.top.findNode("colorizedProgressBar")
m.video = m.top.findNode("myVideoNode")
m.video.enableUi = false
m.video.notificationInterval = 1
m.video.seekMode = "accurate"
m.video.observeField("position", "onPositionChanged")
sub onPositionChanged()
position = m.video.position
m.colorizedProgressBar.width = ((m.video.position + 1) / m.video.duration) * m.emptyProgressBar.width
end sub
And then add a indicator that follows the current position
