"Roj", the Open Poster "moley6knipe" asked for the way of handling to delete "an entry from the recently used lists within mp3tag, such as the one that appears when you type something into e.g. the field: box in the "replace" action.
This can be done by using keyboard shortcut [Shift]+[Del].
This information is retrievable from the manual.
You see that there is a proper solution regarding the initial question.
One step further.
To delete all history entries from an item list at once, the process is simply the same.
Hold the [Shift] key and press the keys [Del] and [CursorDown] alternately until the whole list is empty.
For better overview what item to delete you can expand the item list by [Alt]+[CursorDown]. Collapse the itemlist by [Alt]+[CursorUp].
There is an always surprising and disturbing caveat in M3tag's item list management:
the current dialog cannot be closed when the item list is empty.
If you escape the dialog at this state, then your changes from before will not be stored permanently.
So you have to put in some dummy entry and try to leave the dialog by pressing [OK] button.
In case of the action "Replace" dialog, you can put in the field name DUMMY and put a dot character into the input fields "Original" and "Replace by" and then press [OK]. Then the changes from before will be stored permanently.
Sure, now there is a new entry in the list, you do not want ever.
You can repeat this process until you get gray hair.
Yes, rather bad design.
My recommendation: Swallow this toad and focus on the good side of Mp3tag.
I've been waiting since a few years. I am sure, time will come for the badly needed change regarding a proper useful item list management.