Maybe a dedicated button would be useful as it’s easier to discover and may reduce friction. However, until then:
As you mention a mouse, it seems that you are talking about the PC version of the remote. If so, be aware that there are much more powerful/convenient ways to multi-select than long-pressing every item and clicking every checkmark.
Select multiple individual albums by holding the Ctrl on Windows / Command on Mac key and then clicking (short left click) each item to add to the selection.
You also select ranges easily:
- Select an album (with long click, Ctrl+Click or rightclick) to select the first in the range
- Hold Shift and click the last in the range, all between will be selected.
You can also select several ranges at once by repeating this with different range start points.
Optionally, add to the multi-selection with additional clicks on individual items.
(This multi-selection works with all kinds of things like albums, tracks, artists. You can then apply, for instance, an edit (like credits) to all of them at once.)
These are not possible on iOS / Android as multi-selection there requires to check every item, and there is no range selection as far as I know. However, this applies not only to the new feature but everywhere.