A setting worth understanding before you ever need it, because by the time you need it, it is too late to read about it.
Where
Go to Mollie Payments, then Options, and find Delete data on uninstall.
The setting
Delete all plugin data when the plugin is removed.
This decides whether your transactions, settings and API keys are removed when you fully uninstall the plugin.
The reassurance, in the plugin’s own words
Data is never deleted during an update.
This only applies when you fully delete the plugin, through Plugins, then Delete.
So updating the plugin is safe. It has always been safe. Nothing you have is at risk when a new version arrives, and you do not need to back anything up before updating.
Switched off is the safe choice
Leave it off, and your data survives even a full uninstall. If you ever reinstall, everything is still there.
That is what most people want, and it is why it is not on by default.
When you would switch it on
Handing a site to a client who should not inherit your data.
Decommissioning a site properly, where leaving payment records behind would be untidy or non-compliant.
Testing, on a site you are going to throw away.
Deactivating is not deleting
Worth being clear, because the words get used loosely.
Deactivating the plugin switches it off. Nothing is deleted. Your data waits for you.
Deleting the plugin removes it from WordPress, and this setting decides what happens to the data.
If you are troubleshooting and someone tells you to deactivate the plugin, that is safe. It is not the same as deleting it.