Possibility to select multiple files in manage files menu

[ThiloteE]

Describe the bug :
It is not possible to select multiple files in the "Manage files (Alt + F)" menu. I want to delete files and it is tedious having to delete them one by one.

There is a workaround to press the trash button, which opens a separate window that allows one to select and delete multiple files at once. Is there a reason why this functionality is hidden in a separate window accessible by a button and not part of the main screen instead? It took me way too long to find that button. At first I simply thought it's only possible to delete one file at a time.

To Reproduce :

1. Press Alt + F
2. Try to shift + Arrow up/down or shift + left-click on files --> Result: Doesn't work.

Expected behavior :

1. Files will be selected with shift + arrow up/down or left click
2. and if there is a right-click, it is possible to delete all of them in one go.

Screenshots :

Desktop (please complete the following information):
Windows 10
QualCoder 3.8.2

[ccbogel]

HI. Originally the one row selection was to reduce some errors. I will have a look at implementing multiple selection, and try to test if that introduces other errors.