I’m not sure what language you are using on openstreetmap.org, you may have translated the message incorrectly. I think you are referring to the “still editing” message.

When you save some changes in Potlatch 2, then the changeset (which is a group of edits) will remain open. This means you can continue with more changes, then save them in the same changeset. In Potlatch 2, you can close the changeset by pressing “C”. Or the changeset will close automatically after an hour.
So usually you don’t need to worry about it, just save your edits in Potlatch. Note if you are doing different types of edits, it may be helpful to group them into separate changesets, then you can add a relevant comment for each part.