This documentation is not using the current rendering mechanism and will be deleted by December 31st, 2020. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
Inside the extension manager you are able to change the following options in configuration:
If set, most of checkboxes in the frontend plugin will turn into selectboxes, so you can choose "from TypoScript"
By default all boolean configuration options are represented by checkboxes in the frontend plugin.
They override always the TypoScript settings via constants/setup. If you want to be able to define all the settings (not only the not boolean) just once per template e.g. in constant editor, you have to set useSelectInsteadCheckbox to 1.
In this case the default option in the selectbox is "from TypoScript". But you can still override the TS settings by choosing one of the other options “Yes” or “No”.
In the screenshots below you can see an example of the difference of the output in the frontend plugin.
UseSelectInsteadCheckbox = 1 // useSelectInsteadCheckbox = 0