Keyboard shortcut for mouse left-click?

My keyboard has two hotkeys under the spacebar. You can set what you want them to do by entering a key combination in the settings. I set the right hotkey to simulate mouse right-clicking by using the key combination Shift + F10. I’m now trying to set the left hotkey to simulate mouse left-clicking by using a key combination, but I can’t find what it is anywhere.

Some say the number pad with /5, and while that does work if I press them manually, I can’t set that in my settings because the keys have to be within the main keyboard.

I don’t want to install any third party software. Is there a plain old basic built-in combination like Shift + 10? If not, why does Microsoft have to do irritating things like not including a left-click keyboard combination for no reason? Thanks.