I entered the names with no comma between the town, county, country etc
I backtracked and corrected the entries.
However it still remembers the old unused ‘Place’ name. Besides which I have to enter “Leicester, Leicesters” before the correct one appears, “Leicester, Leicestershire, England, United Kingdom”.
In RM10 (you didn’t say which version) on the “Places” view select the place you want to retain and right click, select merge places. A screen will open that will allow you to tick all the places that you want to merge into the place to be kept. It will keep all the place details and move their tags into the place being retained and merge all the places into the place being retained.
This is pretty much the standard process for cleaning up you “Places” list after you split the place details from the place also.
This is just a little followup to the excellent message from BobC The reason that editing the place list works to remove the undesirable place names as hints is that when you are typing in place names, RM searches your place list itself to provide you with hints for the new place name you are entering. So by removing the undesirable place names from the place list, the undesirable place names are no longer available to RM to provide to you as hints.
The reason for merging the undesirable place names into desirable place names rather than just deleting the undesirable place names is that some of the undesirable place names may still be in use. In addition, and as BobC mentioned, some of the undesirable place names may have Place Details that you do not wish to lose.
Finally, if the spelling of the undesirable place names and of the desirable place names with which you want to merge are similar enough, it can be very helpful to filter the place list during the merge process using some common portion of the undesirable and desirable place names. That will help to focus your merge operations just on the place names of interest.
Don’t forget to go to Places, 3 dots, Show unused places and check for locations no longer linked to a person. You can deleted the places from that location, too.