If you want to do custom work you can make an order here:
This is a SharePoint Framework webpart where site collection administrator can give permission to any group within the site using one click. No need to go each group page and add users for that group. You can easily show all groups in this webpart and add users from the people picker and check the checkbox to add user for the specific group. Also you can easily remove users from the group by uncheck the checkbox.
We use ReactJS for this webpart.
Supported Version: SharePoint Online, SharePoint 2019 On-Premises