Right now a left double click in the Filter box will select only one word / continuous set of strings: 1 click - focus is made 2 clicks - nearest word is selected
I propose to adjust that behavior: 3 clicks - whole expression is selected
Right now this has to be done manually, by either pressing the left button and then dragging the mouse pointer horizontally or by pressing CTRL + A
Alternatively instead of 3 quick clicks it could be a second quick double click, performed any time after the first double click selects one word
Or if the cursor is not in the filter-line you can click outside the line in the surrounding of the filter like on "Filter:" or anywhere in the filter-line-sorrounding.
But not if you already have selected a word with a double click or the cursors is in the Filter. Then you have to click elsewhere first and only the clicking on the "Filter" sign will select everything