If a user's number of files in the main window exceeds user's screen height plus the overall width of columns exceeds user's screen width, then such user is unable to select those files with a mouse - unless user uses also a keyboard; i.e. holding down the SHIFT or CTRL key. And an alternative solution in such situation is grab right side of one or more columns and reduce their widths; or turn off some of the columns
And at the same time if a user in the main window clicks left mouse button and moves the pointer, nothing happens [which is indicated by a change of pointer into icon of a crossed circle]. And so- why not make such move draw an area, from which files will be marked for selection? If I am not mistaken, what I am proposing is the default behavior of Explorer in Windows 10
Such behavior is also possible in file manager FreeCommander. But in this file handler it is also possible to determine just how exactly selection of files with a pointer should work, as there are some options for it- maybe such configuration feature in regard to this could also be implemented in Mp3tag?
And if selecting of files with just one push down and then release of the left mouse button is impossible, then maybe the middle button could be used for that?
All in all what I am saying is that the current files selection behavior of Mp3tag is not user friendly, if its user for whatever reason is not using a keyboard. Current behavior can require from user additional clicks and and is simply annoying on a day-to-day basis
I think that in MP3tag it is not clear what you select with a catch rectangle:
Is it the (whole) column?
Is it the (whole) row in the table?
In the refernced WE it is clear: in the details view it only allows to select rows.
The catch rectangle then works only for adjacent files - files that are apart from each other have to be selected with key-support from the keyboard as well.
Coming back to MP3tag:
In MP3tag you can move files in the list up and down - something that the WE does not allow.
That a simple drag&drop does not do anything in the file list is owed to the fact that you d&d from the file list to other applications.
So, the catch rectangle is out as it is not clear what it means in respect to selection.
The simple click, then d&d has a function, admittedly not the one that is suggested in the OP.
Comng to the columns: the only function that is available for columns can be found in the column headers.
The columns can be re-arranged wih drag&drop - so a drag of a single column does not mean that a catch rectangle should be created but moves the column along with the mouse cursor.
A click on the column triggers the sorting.
So right now I think that all interactions between the mouse and the GUI elements are already used up and no other function could be added unless already implemented functions are lost.
Without a keyboard, how are you possibly editing the content of any tags?
Mouse controls are pretty versatile, but ultimately have limited ability when it comes to working with text, other than perhaps a right-click to cut/copy/paste. Hence the reason a modern keyboard has 100+ keys. The functions you mention in the OP are universally practiced standards, using the shift, alt, and control keys to enable enhanced selection alternatives along with a mouse. Coming up with new ways to do the same, suggesting a keyboard isn't available, seems a complete waste of time to me when the keyboard is an essential tool. At least when it comes to mp3tag.
So please remind me, what does the middle button do in Mp3tag?
But with predefined actions of course. And also the Move and Copy features available under the right click menu can be utilized without keyboard
For the longest time it has been my modus operandi to listen to, evaluate and make various decision in regards to my music [and new potential music] when am lying in bed and reading, be it a paper book or a hugely enlarged wiki article. [And it was only recently that I finally was able to get my hands on a small, wireless keyboard [and with lighted buttons] that alleviates a lot of my issues when using my computer when not sitting in front of its monitor- but still selecting more than one file in Mp3tag even with such device is problematic as it requires from me constant taking of it into my other hand and then putting it away to free it
I guess that you will have to hurt or even loose one of your hands to see things differently
The middle mouse button is not defined by a standard, it is something optional.
In many cases it is a wheel that eases scrolling.
In many other cases it is freely configurable in the mouse driver options.
So, it should be easy for you, if you have such a mouse, so set the middle mouse button to function like Shift or Ctrl or Alt.
But MP3tag should not rely on functions that are not supported standard by the OS.