Question about Musescore 3

Hi,
I am using Musescore 3 for the first time.
Due to using the previous versions for quite some time, I am mostly familiar with most of the features.
However, one thing I cannot seem to manage is to change the instrument names to the left of the page.

Whether I click or double click on them, nothing happens.
Any idea whether this is a bug or whether I am doing something wrong (maybe because something in the program changed)?

Thank you in advance.