WooCommerce does not provide plus and minus buttons to easily increase or decrease the quantity of a product, which can create hassle for customers. To make this process smoother, the Single Product Page Customizer plugin offers an option to enable Plus/Minus buttons for the quantity field.
If “Enable plus minus button” is checked, then the plus minus button shows for quantity change from the single product page.

Before enabling the plus minus button on the single product page.

After enabling the plus-minus button on the single product page by using this plugin.