▪Picker view manipulation:

-MG-Picker view adopt the very similar rules as you interactive with Maya's 3d viewport:

MMB: Pan the view, with/without the alt key.

ALT + RMB: Zoom in/out the view.

CTRL + ALT + LMB: Box zoom in the view / Reset to its default size.

F Key: Frame on selected picker items, zoom out to show all the picker items if no items selected.

Space Key: If you are in multiple-viewport layout, press and release space key to maximize and hide other area, space key again to restore. Just like what maya does to its 3d viewport.

-Beside the rules above, extra convenient view manipulation rules are also adopted:

ALT + RMB Double clicking: Reset view to its default size.

MMB Scrolling: Depending on the width/height ration of the picker content, this will pan the view in horizontal/vertical direction.
If you hold ALT key while MMB scrolling, will pan in different direction other than normal MMB scrolling.

Ctrl + MMB Scrolling: Zoom in/out the view.

0~9 Key: Frame & Pan the view to show the picker panel with the panel index number the same as the hotkey.
You can use ~ key to replace the 0 key.

-Multiple picker view:

-Usually a picker tab stands for a Asset or a character. To View multiple characters at the same time:

LMB click on  layout switch button at the top right corner of picker view, select one of the predefined viewport layout.
Using a layout other than "Single", more picker views could be displayed in the ui, and you can LMB drag tabs and drop them to the new layout area, or just double clicking on the new layout area,
to open a picker file into that area.