is there any way to make my texture bar grow vertically instead of horizontally?
Welcome to the forums @jackhen!
You can use a TextureProgress node, and then set the fill mode to either top-to-bottom or bottom-to-top to get a vertical progress bar.
What you can do is change its fill mode, to the TopToBottom setting that Godot has bestowed.
Then you may set it's size as you fit, you might wanna play with its size flags a bit.