There aren’t any buttons in obsidian. But you can use hotkeys to format selected text bold or italic (there is no underline in markdown). You can check and alter all hotkeys in the settings.
By the way, I dont’ really see the advantages of having toolbar buttons for bullet points, quotes or headings - that actually is, in my view, one of the powers of markdown: formatting is much faster and easier…
If you’re directly typing, yes. But I often either transfer notes from other apps like notepad++ or type out everything first then come back to apply my formatting.
At that point it’s much easier to highlight the relevant sections and press a button to apply needed formatting than doing it manually. (because mouse navigation is faster than keyboard navigation & keeping a hand on the keyboard for the shortcut combinations just gets in the way)