Hi Max, you can do that by setting a selection filter - that will restrict selection actions to only work on the filtered items.

To set the selection filter, go to the Styles section of the Scene browser, and hold down the Ctrl key and click on the right-hand side of the item, right where the selection indicator dot is at. See here for a screenshot of where to click: http://moi3d.com/forum/index.php?webtag=MOI&msg=4438.21

When you do the Ctrl + click on that spot a little filter icon will appear on that item. While that filter is active any kind of selection action you do including window selection, select all, etc... will only target the filtered items.

When you're done doing the targeted selection either Ctrl + click on it again or just press Escape once to clear the current filter.

You can also set multiple filters including across different sections of the scene browser, like for example you can set a filter on Types > Curves, as well as on a style, so that when you window select after that you will only then be targeting curves on that style and not surfaces or solids on that style.

Hope that helps,

- Michael