1) I think that must have inadvertently, clicked on something which has changed my library tree view to what is shown in the screenshot below.

Can anyone please tell me how to get rid of the black/grey area between my library tree and the part of the screen that displays the disc/file details?
I've tried everything that I can think of but with no success.
2) My second query is more of an irritant, rather than a problem and I would not have posted about it if I'd not had another query as well.
When I am copying and pasting (for example) composer details MM will not allow me to insert a semi colon after any preceding names prior to pasting - it just removes it, which means that I have to go back and then insert and it is then accepted by MM.
I can copy/paste a string of names with semi colons between them but not insert them if I am adding names one at a time.
I'm sure that this never used to be the case, can anyone please tell me why this should now be happening?
Any help would be, very much, appreciated.
Thanks in advance.