Regarding your issue - where you want to limit the checkboxes option what fields you have and how you want to configure it. Can you please share all required details with example and I would be happy to help. Few screenshots may be helpful to understand your issue.
let me try to explain. In the backend Toolset -> edit group I have a field type checkboxes called COLOUR and I have added around 170 colours as options. If I try to add another one it seems to not work because it delete a previously inserted option.
Is there a limit in the number of options a checkbox field may have?
Thanks,
Gianni
There is no such limit but as per the issue you shared it seems on your server it reaches the limit of "max_input_vars ". I asked you to share debug information you you did not otherwise it was helpful to identify the issue.