Here is how you replicate this time and clicks stealing bug:
0] Make the Tag Panel visible
1] Load for example 10 files that does not have any content in tag fields
2] Select the first file from the list in the main window
3] Click for example "ALBUM" tag field, so that you can edit it. You need of course have it displayed as one of the Columns
4] Write to it "New Title". Do not press Enter
5] Then press SHIFT and select any number of files with mouse pointer. You should have now at least two files being selected, one of which is the one that was edited. And you should see the edited content as already being saved- the ALBUM column should display for the first file the "New Title" which you have just written
6] Now go to Tag Panel with mouse pointer, navigate to the triangle mini-icon in the ALBUM tag field and click it
7] You should see only "< blank >" and "< keep >". And this is the bug
At executing point 5 the data has already been accepted and even displayed by Mp3tag- in the main window where the files are listed. So there is no reason for the Tag Panel not to be aware of this. The list should already contain
< blank >
< keep >
New Title
But instead of this Mp3tag requires from user to click somewhere else after changing / entering new data in the main window, loosing selection of the first file [the one that had the data changed]. Because only then making a selection of files have a sense- in that the Tag Panel will display "New Title" as an option [under condition the file with this "New Title" will be re-selected]. So the user cannot speed up process of renaming album by changing it just one time in the main window and then simply then selecting all of the file from that album and neatly navigating to Tag Panel for the purpose of distributing [coping] the new name on all of the files by selecting there the new version from the drop down list- because it is not [yet] there [as it should]