Hey everyone,
I am currently beta testing a binding that will be released in one of the next releases of openhab.
Now I am curious how the migration would be done for that case.
Would I just install the binding and remove the jar of the manual installation?
Opposite way round…
Remove the jar and then install from the ui 
Will the things be kept by openhab? 
Yes, unless you delete them. The only time I believe they’ll be an exception to this is if something like the following happens:
Openhab2 had a binding intesisbox (custom jar)
Things were created for this binding.
IntesisHome was then added to the binding
Binding was renamed to intesis for OH3
Thank you so much