Need help with customizing pointer/thumb of vertical slider

Pretty new to JUCE and coding, im trying to customize the thumb/pointer for my vertical horizontal sliders in the Lookandfeel class but cant see to get the draw pointer codes correct.
My thumb is just a very simple rounded rectangle shape, if anyone could giveme some tips that would be really useful thanks!!

All the relevant methods you can override to customise the look of your slider are listed here: JUCE: Slider::LookAndFeelMethods Struct Reference
Some of those are just helpers being used by drawLinearSlider.

drawLinearSliderThumb draws your thumb.

getSliderThumbRadius is used to adjust the overall slider layout so there is enough space for your thumb.