I would use hooks in order to hold items in mesh bags instead of changing the rod. You can get suction cup type of soap dish style small shelves at the kitchen/bath stores.
Here are a couple of products you could ADD to the shower, leaving the towel bar
This comes in different metal finishes
This in different finishes and sizes
Your other option is to Google "how to remove ceramic tile towel bar" and to take out the entire thing. Then, you'll need to figure out what/how to install something different. Good luck! 😎
I would leave the towel bar alone, only because it is 'ceramic' and that is not a home job.You will need a professional to remove, and also find new white tiles to replace....What you can do is put a shelf above the towel bar, say 6 inches higher....Onto the wall.
First - What do you want the shelf to hold?
Mount your shelf just above the wall tile and leave the towel rod alone.
If you take down the towel bar, it will probably take tiles with it because of the adhesive, making a replacement necessary. A shelf above the bar would work or simply hang things from the bar.